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Papers by Alan Howe

Research paper thumbnail of Protein Kinase A is a Functional Component of Focal Adhesions

bioRxiv (Cold Spring Harbor Laboratory), Aug 19, 2023

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Research paper thumbnail of Therapeutic implications for ovarian cancer emerging from the Tumor Cancer Genome Atlas

Translational cancer research, Feb 13, 2015

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Research paper thumbnail of The focal adhesion protein talin is a mechanically-gated A-kinase anchoring protein (AKAP)

The cAMP-dependent protein kinase (Protein Kinase A; PKA) is a ubiquitous, promiscuous kinase who... more The cAMP-dependent protein kinase (Protein Kinase A; PKA) is a ubiquitous, promiscuous kinase whose activity is focused and specified through subcellular localization mediated by A-kinase anchoring proteins (AKAPs). PKA has complex roles as both an effector and a regulator of integrin-mediated cell adhesion to the extracellular matrix (ECM). Recent observations demonstrate that PKA is an active component of focal adhesions (FA), intracellular complexes coupling ECM-bound integrins to the actin cytoskeleton, suggesting the existence of one or more FA AKAPs. Using a combination of a promiscuous biotin ligase fused to PKA type-IIα regulatory (RIIα) subunits and subcellular fractionation, we identify the archetypal FA protein talin1 as an AKAP. Talin is a large, mechanosensitive scaffold that directly links integrins to actin filaments and promotes FA assembly by recruiting additional components in a force-dependent manner. The rod region of talin1 consists of 62 α-helices bundled into ...

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Research paper thumbnail of Protein Kinase A Activity In The Leading Edge of Migrating Cells Is Dependent On The Activity of Focal Adhesion Kinase

ABSTRACTProtein Kinase A (PKA) is a pleiotropic serine/threonine kinase whose localized and dynam... more ABSTRACTProtein Kinase A (PKA) is a pleiotropic serine/threonine kinase whose localized and dynamic activity is required for cellular migration. Several cell types have shown robust PKA activity in the leading edge during migration. This activity is regulated by changes in actomyosin contractility, but the mechanism of the mechanochemical regulation of PKA remains unclear. Our ongoing investigation into this mechanism led us to discover a novel relationship between PKA and the non-receptor tyrosine kinase Focal Adhesion Kinase (FAK). Here, we find that while inhibition of actomyosin contractility leads to a relatively slow decrease in total cellular levels of phosphorylated FAK over tens of minutes, it decreases the focal adhesion-associated pool of both phospho-FAK and phospho-paxillin within two minutes, similar to the timing of the effect of inhibition of contractility on leading edge PKA activity. We then show that pharmacologic inhibition of FAK rapidly decreases leading edge P...

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Research paper thumbnail of Protein Kinase A in cellular migration—Niche signaling of a ubiquitous kinase

Frontiers in Molecular Biosciences

Cell migration requires establishment and maintenance of directional polarity, which in turn requ... more Cell migration requires establishment and maintenance of directional polarity, which in turn requires spatial heterogeneity in the regulation of protrusion, retraction, and adhesion. Thus, the signaling proteins that regulate these various structural processes must also be distinctly regulated in subcellular space. Protein Kinase A (PKA) is a ubiquitous serine/threonine kinase involved in innumerable cellular processes. In the context of cell migration, it has a paradoxical role in that global inhibition or activation of PKA inhibits migration. It follows, then, that the subcellular regulation of PKA is key to bringing its proper permissive and restrictive functions to the correct parts of the cell. Proper subcellular regulation of PKA controls not only when and where it is active but also specifies the targets for that activity, allowing the cell to use a single, promiscuous kinase to exert distinct functions within different subcellular niches to facilitate cell movement. In this ...

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Research paper thumbnail of Therapeutic implications for ovarian cancer emerging from the Tumor Cancer Genome Atlas

Translational cancer research, 2015

With increasing insights into the molecular landscape of ovarian cancer, subtypes are emerging th... more With increasing insights into the molecular landscape of ovarian cancer, subtypes are emerging that might require differential targeted therapies. While the combination of a platinum and a taxane remains the standard of care, newer therapies, specifically targeted to molecular anomalies, are rapidly being tested in various cancers. A major effort to better understand ovarian cancer occurred through the Cancer Atlas Project. The Catalogue of Somatic Mutations in Cancer (COSMIC) is a database that collates mutation data and associated information extracted from the primary literature. The information from the Cancer Genome Atlas (TCGA) and the International Cancer Genome Consortium (ICGC), which systematically analyzed hundreds of ovarian cancer, are included in COSMIC, sometimes with discordant results. In this manuscript, the published data (mainly from TCGA) on somatic high grade papillary serous ovarian cancer (HGSOC) mutations has been used as the basis to propose a more granular...

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Research paper thumbnail of The focal adhesion protein talin is a mechanically gated A-kinase anchoring protein

Proceedings of the National Academy of Sciences of the United States of America, Mar 21, 2024

There is increasing interest in the ability of proteins involved in cell adhesion to convert mech... more There is increasing interest in the ability of proteins involved in cell adhesion to convert mechanical force into altered biochemistry. Cellular signal transduction is most often conducted through multiprotein scaffolds that consolidate, localize, and specify signaling inputs and outputs. This report bridges these fields by identifying an interaction between talin, a mechanosensitive adhesion protein, and PKA, a pleiotropic kinase with myriad cellular targets. Together, these observations form the foundation for a mechanotransduction pathway that utilizes forcedependent changes in protein conformation to establish a solid-state signaling complex well positioned to couple cellular tension to cellular communication.

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Research paper thumbnail of Stress and matrix-responsive cytoskeletal remodeling in fibroblasts

Journal of Cellular Physiology, Oct 4, 2012

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Research paper thumbnail of Localized Energy Sensing Targets Mitochondria to the Leading Edge of Migrating Cells

Free Radical Biology and Medicine, Nov 1, 2014

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Research paper thumbnail of Live free or die: Stretch-induced apoptosis occurs when adaptive reorientation of annulus fibrosus cells is restricted

Biochemical and Biophysical Research Communications, May 1, 2012

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Research paper thumbnail of AMPK activity regulates trafficking of mitochondria to the leading edge during cell migration and matrix invasion

Molecular Biology of the Cell, Sep 1, 2016

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Research paper thumbnail of Abstract 5224: Non-canonical activity of threonyl-tRNA synthetase promotes angiogenesis and invasion in a mouse model of ovarian cancer

Despite clear connections between the tumor microenvironment and ovarian cancer invasion, the und... more Despite clear connections between the tumor microenvironment and ovarian cancer invasion, the underlying molecular mechanisms remain elusive. We have recently shown that the protein synthesis regulator threonyl-tRNA synthetase (TARS) has a unique extracellular angiogenic activity separate from its canonical function. Secreted TARS promotes endothelial cell migration and tube formation, and a selective TARS inhibitor, BC194, disrupts normal vessel development in zebra fish and chick embryo models. TARS expression also correlates with tumor stage and angiogenesis in human ovarian cancer. The objective of this study was to validate the biological and clinical relationship between TARS and ovarian tumor progression using a syngenic mouse model of epithelial ovarian cancer. Tumors were initiated by intraperitoneal injection of ID8 mouse ovarian cancer cells, and tumors formed at 4-6 weeks were scored for invasiveness and analyzed by immunostaining for TARS expression and microvascular density. To test the hypothesis that overexpression of TARS promotes invasion, cells were stably transfected with a TARS expression plasmid prior to injection. To test the hypothesis that TARS inhibition reduces tumor invasion, animals harboring ID8 tumors were treated with the high-affinity TARS inhibitor BC194. We found that TARS levels were elevated in ovarian tumors as compared with normal ovarian tissue. Overexpression of TARS in ID8 cells also resulted in enhanced invasiveness and microvascular density of the resulting tumors (p = 0.026). Preliminary results also indicated that inhibition of TARS by BC194 treatment reduced tumor angiogenesis and growth (p = 0.005) without observed toxicities in the animals. Overall, these results show that modifying TARS expression or activity can affect in vivo ovarian tumor angiogenesis and progression. These results encourage further study of TARS as a regulator of the tumor microenvironment and as a possible target for diagnosis and treatment of ovarian cancer. Citation Format: Peibin Wo, Theresa Wellman, Alan Howe, Christopher Francklyn, Karen M. Lounsbury. Non-canonical activity of threonyl-tRNA synthetase promotes angiogenesis and invasion in a mouse model of ovarian cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5224. doi:10.1158/1538-7445.AM2015-5224

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Research paper thumbnail of Spatial restriction of α4 integrin phosphorylation regulates lamellipodial stability and α4β1-dependent cell migration

Carolina Digital Repository (University of North Carolina at Chapel Hill), 2003

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Research paper thumbnail of The mechanical microenvironment regulates ovarian cancer cell morphology, migration, and spheroid disaggregation

Scientific Reports, 2018

There is growing appreciation of the importance of the mechanical properties of the tumor microen... more There is growing appreciation of the importance of the mechanical properties of the tumor microenvironment on disease progression. However, the role of extracellular matrix (ECM) stiffness and cellular mechanotransduction in epithelial ovarian cancer (EOC) is largely unknown. Here, we investigated the effect of substrate rigidity on various aspects of SKOV3 human EOC cell morphology and migration. Young’s modulus values of normal mouse peritoneum, a principal target tissue for EOC metastasis, were determined by atomic force microscopy (AFM) and hydrogels were fabricated to mimic these values. We find that cell spreading, focal adhesion formation, myosin light chain phosphorylation, and cellular traction forces all increase on stiffer matrices. Substrate rigidity also positively regulates random cell migration and, importantly, directional increases in matrix tension promote SKOV3 cell durotaxis. Matrix rigidity also promotes nuclear translocation of YAP1, an oncogenic transcription ...

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Research paper thumbnail of Localized Energy Sensing Targets Mitochondria to the Leading Edge of Migrating Cells

Free Radical Biology and Medicine, 2014

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Research paper thumbnail of Fibroblast cytoskeletal remodeling contributes to connective tissue tension

Journal of Cellular Physiology, 2011

The visco‐elastic behavior of connective tissue is generally attributed to the material propertie... more The visco‐elastic behavior of connective tissue is generally attributed to the material properties of the extracellular matrix rather than cellular activity. We have previously shown that fibroblasts within areolar connective tissue exhibit dynamic cytoskeletal remodeling within minutes in response to tissue stretch ex vivo and in vivo. Here, we tested the hypothesis that fibroblasts, through this cytoskeletal remodeling, actively contribute to the visco‐elastic behavior of the whole tissue. We measured significantly increased tissue tension when cellular function was broadly inhibited by sodium azide and when cytoskeletal dynamics were compromised by disrupting microtubules (with colchicine) or actomyosin contractility (via Rho kinase inhibition). These treatments led to a decrease in cell body cross‐sectional area and cell field perimeter (obtained by joining the end of all of a fibroblast's processes). Suppressing lamellipodia formation by inhibiting Rac‐1 decreased cell body...

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Research paper thumbnail of Distinct Mechanisms Mediate the Initial and Sustained Phases of Integrin-mediated Activation of the Raf/MEK/Mitogen-activated Protein Kinase Cascade

Journal of Biological Chemistry, 1998

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Research paper thumbnail of S1687 Serotonin Transporter Function and Expression Are Up-Regulated By a PKA-Independent cAMP Signaling Pathway in Intestinal Epithelial Cells

Gastroenterology, Apr 1, 2008

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Research paper thumbnail of Protein Kinase A activity is regulated by actomyosin contractility during cell migration and is required for durotaxis

Dynamic subcellular regulation of Protein kinase A (PKA) activity is important for the motile beh... more Dynamic subcellular regulation of Protein kinase A (PKA) activity is important for the motile behavior of many cell types, yet the mechanisms governing PKA activity during cell migration remain largely unknown. The motility of SKOV-3 epithelial ovarian cancer (EOC) cells has been shown to be dependent on both localized PKA activity and, more recently, on mechanical reciprocity between cellular tension and extracellular matrix (ECM) rigidity. Here, we investigated the possibility that PKA is regulated by mechanical signaling during migration. We find that localized PKA activity in migrating cells rapidly decreases upon inhibition of actomyosin contractility (specifically, of myosin ATPase, ROCK (Rho kinase), or MLCK (myosin light chain kinase) activity). Moreover, PKA activity is spatially and temporally correlated with cellular traction forces in migrating cells. Additionally, PKA is rapidly and locally activated by mechanical stretch in an actomyosin contractility-dependent manner....

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Research paper thumbnail of Aminoacyl-tRNA synthetase dependent angiogenesis revealed by a bioengineered macrolide inhibitor

Scientific reports, Jan 14, 2015

Aminoacyl-tRNA synthetases (AARSs) catalyze an early step in protein synthesis, but also regulate... more Aminoacyl-tRNA synthetases (AARSs) catalyze an early step in protein synthesis, but also regulate diverse physiological processes in animal cells. These include angiogenesis, and human threonyl-tRNA synthetase (TARS) represents a potent pro-angiogenic AARS. Angiogenesis stimulation can be blocked by the macrolide antibiotic borrelidin (BN), which exhibits a broad spectrum toxicity that has discouraged deeper investigation. Recently, a less toxic variant (BC194) was identified that potently inhibits angiogenesis. Employing biochemical, cell biological, and biophysical approaches, we demonstrate that the toxicity of BN and its derivatives is linked to its competition with the threonine substrate at the molecular level, which stimulates amino acid starvation and apoptosis. By separating toxicity from the inhibition of angiogenesis, a direct role for TARS in vascular development in the zebrafish could be demonstrated. Bioengineered natural products are thus useful tools in unmasking the...

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Research paper thumbnail of Protein Kinase A is a Functional Component of Focal Adhesions

bioRxiv (Cold Spring Harbor Laboratory), Aug 19, 2023

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Research paper thumbnail of Therapeutic implications for ovarian cancer emerging from the Tumor Cancer Genome Atlas

Translational cancer research, Feb 13, 2015

Bookmarks Related papers MentionsView impact

Research paper thumbnail of The focal adhesion protein talin is a mechanically-gated A-kinase anchoring protein (AKAP)

The cAMP-dependent protein kinase (Protein Kinase A; PKA) is a ubiquitous, promiscuous kinase who... more The cAMP-dependent protein kinase (Protein Kinase A; PKA) is a ubiquitous, promiscuous kinase whose activity is focused and specified through subcellular localization mediated by A-kinase anchoring proteins (AKAPs). PKA has complex roles as both an effector and a regulator of integrin-mediated cell adhesion to the extracellular matrix (ECM). Recent observations demonstrate that PKA is an active component of focal adhesions (FA), intracellular complexes coupling ECM-bound integrins to the actin cytoskeleton, suggesting the existence of one or more FA AKAPs. Using a combination of a promiscuous biotin ligase fused to PKA type-IIα regulatory (RIIα) subunits and subcellular fractionation, we identify the archetypal FA protein talin1 as an AKAP. Talin is a large, mechanosensitive scaffold that directly links integrins to actin filaments and promotes FA assembly by recruiting additional components in a force-dependent manner. The rod region of talin1 consists of 62 α-helices bundled into ...

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Research paper thumbnail of Protein Kinase A Activity In The Leading Edge of Migrating Cells Is Dependent On The Activity of Focal Adhesion Kinase

ABSTRACTProtein Kinase A (PKA) is a pleiotropic serine/threonine kinase whose localized and dynam... more ABSTRACTProtein Kinase A (PKA) is a pleiotropic serine/threonine kinase whose localized and dynamic activity is required for cellular migration. Several cell types have shown robust PKA activity in the leading edge during migration. This activity is regulated by changes in actomyosin contractility, but the mechanism of the mechanochemical regulation of PKA remains unclear. Our ongoing investigation into this mechanism led us to discover a novel relationship between PKA and the non-receptor tyrosine kinase Focal Adhesion Kinase (FAK). Here, we find that while inhibition of actomyosin contractility leads to a relatively slow decrease in total cellular levels of phosphorylated FAK over tens of minutes, it decreases the focal adhesion-associated pool of both phospho-FAK and phospho-paxillin within two minutes, similar to the timing of the effect of inhibition of contractility on leading edge PKA activity. We then show that pharmacologic inhibition of FAK rapidly decreases leading edge P...

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Research paper thumbnail of Protein Kinase A in cellular migration—Niche signaling of a ubiquitous kinase

Frontiers in Molecular Biosciences

Cell migration requires establishment and maintenance of directional polarity, which in turn requ... more Cell migration requires establishment and maintenance of directional polarity, which in turn requires spatial heterogeneity in the regulation of protrusion, retraction, and adhesion. Thus, the signaling proteins that regulate these various structural processes must also be distinctly regulated in subcellular space. Protein Kinase A (PKA) is a ubiquitous serine/threonine kinase involved in innumerable cellular processes. In the context of cell migration, it has a paradoxical role in that global inhibition or activation of PKA inhibits migration. It follows, then, that the subcellular regulation of PKA is key to bringing its proper permissive and restrictive functions to the correct parts of the cell. Proper subcellular regulation of PKA controls not only when and where it is active but also specifies the targets for that activity, allowing the cell to use a single, promiscuous kinase to exert distinct functions within different subcellular niches to facilitate cell movement. In this ...

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Research paper thumbnail of Therapeutic implications for ovarian cancer emerging from the Tumor Cancer Genome Atlas

Translational cancer research, 2015

With increasing insights into the molecular landscape of ovarian cancer, subtypes are emerging th... more With increasing insights into the molecular landscape of ovarian cancer, subtypes are emerging that might require differential targeted therapies. While the combination of a platinum and a taxane remains the standard of care, newer therapies, specifically targeted to molecular anomalies, are rapidly being tested in various cancers. A major effort to better understand ovarian cancer occurred through the Cancer Atlas Project. The Catalogue of Somatic Mutations in Cancer (COSMIC) is a database that collates mutation data and associated information extracted from the primary literature. The information from the Cancer Genome Atlas (TCGA) and the International Cancer Genome Consortium (ICGC), which systematically analyzed hundreds of ovarian cancer, are included in COSMIC, sometimes with discordant results. In this manuscript, the published data (mainly from TCGA) on somatic high grade papillary serous ovarian cancer (HGSOC) mutations has been used as the basis to propose a more granular...

Bookmarks Related papers MentionsView impact

Research paper thumbnail of The focal adhesion protein talin is a mechanically gated A-kinase anchoring protein

Proceedings of the National Academy of Sciences of the United States of America, Mar 21, 2024

There is increasing interest in the ability of proteins involved in cell adhesion to convert mech... more There is increasing interest in the ability of proteins involved in cell adhesion to convert mechanical force into altered biochemistry. Cellular signal transduction is most often conducted through multiprotein scaffolds that consolidate, localize, and specify signaling inputs and outputs. This report bridges these fields by identifying an interaction between talin, a mechanosensitive adhesion protein, and PKA, a pleiotropic kinase with myriad cellular targets. Together, these observations form the foundation for a mechanotransduction pathway that utilizes forcedependent changes in protein conformation to establish a solid-state signaling complex well positioned to couple cellular tension to cellular communication.

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Research paper thumbnail of Stress and matrix-responsive cytoskeletal remodeling in fibroblasts

Journal of Cellular Physiology, Oct 4, 2012

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Localized Energy Sensing Targets Mitochondria to the Leading Edge of Migrating Cells

Free Radical Biology and Medicine, Nov 1, 2014

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Research paper thumbnail of Live free or die: Stretch-induced apoptosis occurs when adaptive reorientation of annulus fibrosus cells is restricted

Biochemical and Biophysical Research Communications, May 1, 2012

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Research paper thumbnail of AMPK activity regulates trafficking of mitochondria to the leading edge during cell migration and matrix invasion

Molecular Biology of the Cell, Sep 1, 2016

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Research paper thumbnail of Abstract 5224: Non-canonical activity of threonyl-tRNA synthetase promotes angiogenesis and invasion in a mouse model of ovarian cancer

Despite clear connections between the tumor microenvironment and ovarian cancer invasion, the und... more Despite clear connections between the tumor microenvironment and ovarian cancer invasion, the underlying molecular mechanisms remain elusive. We have recently shown that the protein synthesis regulator threonyl-tRNA synthetase (TARS) has a unique extracellular angiogenic activity separate from its canonical function. Secreted TARS promotes endothelial cell migration and tube formation, and a selective TARS inhibitor, BC194, disrupts normal vessel development in zebra fish and chick embryo models. TARS expression also correlates with tumor stage and angiogenesis in human ovarian cancer. The objective of this study was to validate the biological and clinical relationship between TARS and ovarian tumor progression using a syngenic mouse model of epithelial ovarian cancer. Tumors were initiated by intraperitoneal injection of ID8 mouse ovarian cancer cells, and tumors formed at 4-6 weeks were scored for invasiveness and analyzed by immunostaining for TARS expression and microvascular density. To test the hypothesis that overexpression of TARS promotes invasion, cells were stably transfected with a TARS expression plasmid prior to injection. To test the hypothesis that TARS inhibition reduces tumor invasion, animals harboring ID8 tumors were treated with the high-affinity TARS inhibitor BC194. We found that TARS levels were elevated in ovarian tumors as compared with normal ovarian tissue. Overexpression of TARS in ID8 cells also resulted in enhanced invasiveness and microvascular density of the resulting tumors (p = 0.026). Preliminary results also indicated that inhibition of TARS by BC194 treatment reduced tumor angiogenesis and growth (p = 0.005) without observed toxicities in the animals. Overall, these results show that modifying TARS expression or activity can affect in vivo ovarian tumor angiogenesis and progression. These results encourage further study of TARS as a regulator of the tumor microenvironment and as a possible target for diagnosis and treatment of ovarian cancer. Citation Format: Peibin Wo, Theresa Wellman, Alan Howe, Christopher Francklyn, Karen M. Lounsbury. Non-canonical activity of threonyl-tRNA synthetase promotes angiogenesis and invasion in a mouse model of ovarian cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5224. doi:10.1158/1538-7445.AM2015-5224

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Research paper thumbnail of Spatial restriction of α4 integrin phosphorylation regulates lamellipodial stability and α4β1-dependent cell migration

Carolina Digital Repository (University of North Carolina at Chapel Hill), 2003

Bookmarks Related papers MentionsView impact

Research paper thumbnail of The mechanical microenvironment regulates ovarian cancer cell morphology, migration, and spheroid disaggregation

Scientific Reports, 2018

There is growing appreciation of the importance of the mechanical properties of the tumor microen... more There is growing appreciation of the importance of the mechanical properties of the tumor microenvironment on disease progression. However, the role of extracellular matrix (ECM) stiffness and cellular mechanotransduction in epithelial ovarian cancer (EOC) is largely unknown. Here, we investigated the effect of substrate rigidity on various aspects of SKOV3 human EOC cell morphology and migration. Young’s modulus values of normal mouse peritoneum, a principal target tissue for EOC metastasis, were determined by atomic force microscopy (AFM) and hydrogels were fabricated to mimic these values. We find that cell spreading, focal adhesion formation, myosin light chain phosphorylation, and cellular traction forces all increase on stiffer matrices. Substrate rigidity also positively regulates random cell migration and, importantly, directional increases in matrix tension promote SKOV3 cell durotaxis. Matrix rigidity also promotes nuclear translocation of YAP1, an oncogenic transcription ...

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Localized Energy Sensing Targets Mitochondria to the Leading Edge of Migrating Cells

Free Radical Biology and Medicine, 2014

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Fibroblast cytoskeletal remodeling contributes to connective tissue tension

Journal of Cellular Physiology, 2011

The visco‐elastic behavior of connective tissue is generally attributed to the material propertie... more The visco‐elastic behavior of connective tissue is generally attributed to the material properties of the extracellular matrix rather than cellular activity. We have previously shown that fibroblasts within areolar connective tissue exhibit dynamic cytoskeletal remodeling within minutes in response to tissue stretch ex vivo and in vivo. Here, we tested the hypothesis that fibroblasts, through this cytoskeletal remodeling, actively contribute to the visco‐elastic behavior of the whole tissue. We measured significantly increased tissue tension when cellular function was broadly inhibited by sodium azide and when cytoskeletal dynamics were compromised by disrupting microtubules (with colchicine) or actomyosin contractility (via Rho kinase inhibition). These treatments led to a decrease in cell body cross‐sectional area and cell field perimeter (obtained by joining the end of all of a fibroblast's processes). Suppressing lamellipodia formation by inhibiting Rac‐1 decreased cell body...

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Research paper thumbnail of Distinct Mechanisms Mediate the Initial and Sustained Phases of Integrin-mediated Activation of the Raf/MEK/Mitogen-activated Protein Kinase Cascade

Journal of Biological Chemistry, 1998

Bookmarks Related papers MentionsView impact

Research paper thumbnail of S1687 Serotonin Transporter Function and Expression Are Up-Regulated By a PKA-Independent cAMP Signaling Pathway in Intestinal Epithelial Cells

Gastroenterology, Apr 1, 2008

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Protein Kinase A activity is regulated by actomyosin contractility during cell migration and is required for durotaxis

Dynamic subcellular regulation of Protein kinase A (PKA) activity is important for the motile beh... more Dynamic subcellular regulation of Protein kinase A (PKA) activity is important for the motile behavior of many cell types, yet the mechanisms governing PKA activity during cell migration remain largely unknown. The motility of SKOV-3 epithelial ovarian cancer (EOC) cells has been shown to be dependent on both localized PKA activity and, more recently, on mechanical reciprocity between cellular tension and extracellular matrix (ECM) rigidity. Here, we investigated the possibility that PKA is regulated by mechanical signaling during migration. We find that localized PKA activity in migrating cells rapidly decreases upon inhibition of actomyosin contractility (specifically, of myosin ATPase, ROCK (Rho kinase), or MLCK (myosin light chain kinase) activity). Moreover, PKA activity is spatially and temporally correlated with cellular traction forces in migrating cells. Additionally, PKA is rapidly and locally activated by mechanical stretch in an actomyosin contractility-dependent manner....

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Research paper thumbnail of Aminoacyl-tRNA synthetase dependent angiogenesis revealed by a bioengineered macrolide inhibitor

Scientific reports, Jan 14, 2015

Aminoacyl-tRNA synthetases (AARSs) catalyze an early step in protein synthesis, but also regulate... more Aminoacyl-tRNA synthetases (AARSs) catalyze an early step in protein synthesis, but also regulate diverse physiological processes in animal cells. These include angiogenesis, and human threonyl-tRNA synthetase (TARS) represents a potent pro-angiogenic AARS. Angiogenesis stimulation can be blocked by the macrolide antibiotic borrelidin (BN), which exhibits a broad spectrum toxicity that has discouraged deeper investigation. Recently, a less toxic variant (BC194) was identified that potently inhibits angiogenesis. Employing biochemical, cell biological, and biophysical approaches, we demonstrate that the toxicity of BN and its derivatives is linked to its competition with the threonine substrate at the molecular level, which stimulates amino acid starvation and apoptosis. By separating toxicity from the inhibition of angiogenesis, a direct role for TARS in vascular development in the zebrafish could be demonstrated. Bioengineered natural products are thus useful tools in unmasking the...

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