Meenakshi Venkatesan - Academia.edu (original) (raw)

Papers by Meenakshi Venkatesan

The present study had two general aims. The primary purpose was to test whether varying the level... more The present study had two general aims. The primary purpose was to test whether varying the level of threat content in a fear appeal affects attention allocation to the communication. It was predicted that a high threat fear appeal would capture and sustain more attention than a low threat fear appeal and that this increase would facilitate deeper message processing. The second objective was to examine the effect of dispositional and personal relevance factors on the decision to obtain a vaccine that protects against strains of the Human Papillomavirus (HPV). To test these hypotheses, a sample of college women (n = 72) were randomly assigned to listen to either a high threat or low threat fear communication about HPV. A dual-task paradigm was used to measure attention allocation in real-time wherein participants listened to the fear appeal while completing an unrelated visual stimulus discrimination task. Measures of P300, an event-related potential (ERP) component believed to reflect resource allocation, were obtained during message exposure. A follow-up interview was conducted 6-weeks after the experimental session to assess vaccine uptake, information seeking behavior, and knowledge retention about HPV. Women who expressed intentions to obtain the HPV vaccine were more likely to have made plans to get the vaccine or were already vaccinated at the time of iii follow-up (OR = 29.18, CI = 1.53 to 557.53, p < .05). The high threat fear appeal was associated with more knowledge retention about HPV at the time of follow-up than the low threat communication, β = .38, p < .05. The results also suggest that attention allocation during message exposure was positively associated with HPV knowledge retention (β = .23, p < .05) and the likelihood of having obtained or made plans to obtain the vaccine (OR = 1.02, CI = 1.004 to 1.04, p < .05). In the high threat condition, number of sexual partners was positively associated with intentions to consult a doctor about HPV (β = .33, p < .05) and to talk to friends about the vaccine (β = .32, p < .05). However, lack of sexual activity, parental disapproval, and concerns over vaccine safety were the most cited reasons for not wanting or being unsure about the vaccine. The present study has made a significant methodological contribution by incorporating a dualtask paradigm and a real-time measure of attention allocation to assess message processing.

BACKGROUND Digital mental health interventions offer a scalable solution that reduces barriers to... more BACKGROUND Digital mental health interventions offer a scalable solution that reduces barriers to seeking care for clinical depression and anxiety. OBJECTIVE We aimed to examine the effectiveness of a 12-week therapist supported, app-based cognitive behavioral therapy program in improving symptoms of depression and anxiety within 9 months. METHODS A total of 323 participants with mild to moderately severe depression or anxiety were enrolled in a 12-week digital cognitive behavior therapy program. The analysis was restricted to participants who provided at least one follow-up assessment after baseline. As a result, 146 participants (45.2%) were included in the analysis—74 (50.7%) participants completed assessments at 3 months, 31 participants (21.2%) completed assessments at 6 months, and 21 participants (14.4%) completed assessments at 9 months. The program included structured lessons and tools (ie, exercises and practices) as well as one-on-one weekly video counseling sessions with...

Nature Structural & Molecular Biology, Apr 18, 2000

Food Research International

Nature Communications

The sulfonamides (sulfas) are the oldest class of antibacterial drugs and inhibit the bacterial d... more The sulfonamides (sulfas) are the oldest class of antibacterial drugs and inhibit the bacterial dihydropteroate synthase (DHPS, encoded by folP), through chemical mimicry of its co-substrate p-aminobenzoic acid (pABA). Resistance to sulfa drugs is mediated either by mutations in folP or acquisition of sul genes, which code for sulfa-insensitive, divergent DHPS enzymes. While the molecular basis of resistance through folP mutations is well understood, the mechanisms mediating sul-based resistance have not been investigated in detail. Here, we determine crystal structures of the most common Sul enzyme types (Sul1, Sul2 and Sul3) in multiple ligand-bound states, revealing a substantial reorganization of their pABA-interaction region relative to the corresponding region of DHPS. We use biochemical and biophysical assays, mutational analysis, and in trans complementation of E. coli ΔfolP to show that a Phe-Gly sequence enables the Sul enzymes to discriminate against sulfas while retainin...

The sulfonamides (sulfas) are the oldest class of synthetic antibacterial that target the essenti... more The sulfonamides (sulfas) are the oldest class of synthetic antibacterial that target the essential, conserved dihydropteroate synthase (DHPS) enzyme, encoded by folP, through chemical mimicry of its substrate p-aminobenzoic acid (pABA). Resistance has complicated their clinical utility and is widespread in pathogenic species. Resistance is mediated by acquisition of sul genes on mobile genetic elements, which code for the so-called Sul enzymes that are divergent DHPS enzymes with intrinsic sulfa-insensitivity. Even decades after the discovery of this resistance mechanism, its molecular details have not been understood. In this study, we elucidate the molecular basis for intrinsic resistance of Sul enzymes using x-ray crystallography, enzymology, mutagenesis, intrinsic tryptophan fluorescence, antibiotic susceptibility of a contemporary ΔfolP strain, and adaptive laboratory evolution of folP. We show that the active sites of Sul enzymes possess a modified pABA-interaction region bas...

doi:10.1182/blood-2009-07-231191Prepublished online January 14, 2010;2010 115: 2251-2259€€€€Dhe-P... more doi:10.1182/blood-2009-07-231191Prepublished online January 14, 2010;2010 115: 2251-2259€€€€Dhe-Paganon and Aaron D. SchimmerBeheshti Zavareh, Troy Ketela, John C. Reed, David Rose, Jason Moffat, Robert A. Batey, SiranoGronda, Marko Skrtic, Xiaoming Li, Rose Hurren, Xinliang Mao, Meenakshi Venkatesan, Reza G. Wei Xu, Mohsin Ali, Tabitha E. Wood, Derek Wong, Neil Maclean, Xiaoming Wang, Marcela€

Blood, 2010

The proteasomal pathway of protein degradation involves 2 discrete steps: ubiquitination and degr... more The proteasomal pathway of protein degradation involves 2 discrete steps: ubiquitination and degradation. Here, we evaluated the effects of inhibiting the ubiquitination pathway at the level of the ubiquitin-activating enzyme UBA1 (E1). By immunoblotting, leukemia cell lines and primary patient samples had increased protein ubiquitination. Therefore, we examined the effects of genetic and chemical inhibition of the E1 enzyme. Knockdown of E1 decreased the abundance of ubiquitinated proteins in leukemia and myeloma cells and induced cell death. To further investigate effects of E1 inhibition in malignancy, we discovered a novel small molecule inhibitor, 3,5-dioxopyrazolidine compound, 1-(3-chloro-4-fluorophenyl)-4-[(5-nitro-2-furyl)methylene]-3,5-pyrazolidinedione (PYZD-4409). PYZD-4409 induced cell death in malignant cells and preferentially inhibited the clonogenic growth of primary acute myeloid leukemia cells compared with normal hematopoietic cells. Mechanistically, genetic or c...

SummaryCulturing eukaryotic cells has widespread applications in research and industry, including... more SummaryCulturing eukaryotic cells has widespread applications in research and industry, including the emerging field of cell-cultured meat production colloquially referred to as “cellular agriculture”. These applications are often restricted by the high cost of growth medium necessary for cell growth. Mitogenic protein growth factors (GFs) are essential components of growth medium and account for upwards of 90% of the total costs. Here, we present a set of expression constructs and a simplified protocol for recombinant production of functionally active GFs, including FGF-2, IGF-1, PDGF-BB and TGF-β1 in Escherichia coli. Using this expression system, we produced soluble GFs from species including bovine, chicken, and fish. Bioactivity analysis revealed orthologs with improved performance compared to commercially available alternatives. We estimated that the production cost of GFs using our methodology will significantly reduce the cost of cell culture medium, facilitating low-cost pr...

Nature structural biology, 2000

The Rho family GTPases, Cdc42, Rac and Rho, regulate signal transduction pathways via interaction... more The Rho family GTPases, Cdc42, Rac and Rho, regulate signal transduction pathways via interactions with downstream effector proteins. We report here the solution structure of Cdc42 bound to the GTPase binding domain of alphaPAK, an effector of both Cdc42 and Rac. The structure is compared with those of Cdc42 bound to similar fragments of ACK and WASP, two effector proteins that bind only to Cdc42. The N-termini of all three effector fragments bind in an extended conformation to strand beta2 of Cdc42, and contact helices alpha1 and alpha5. The remaining residues bind to switches I and II of Cdc42, but in a significantly different manner. The structure, together with mutagenesis data, suggests reasons for the specificity of these interactions and provides insight into the mechanism of PAK activation.

Protein Science, 2009

Two structurally-related members of the lysosomal mannosidase family, the broad substrate specifi... more Two structurally-related members of the lysosomal mannosidase family, the broad substrate specificity enzyme human lysosomal a-mannosidase (hLM, MAN2B1) and the human core a-1, 6-specific mannosidase (hEpman, MAN2B2) act in a complementary fashion on different glycosidic linkages, to effect glycan degradation in the lysosome. We have successfully expressed these enzymes in Drosophila S2 cells and functionally characterized them. hLM and hEpman were significantly inhibited by the class II a-mannosidase inhibitors, swainsonine and mannostatin A. We show that three pyrrolidine-based compounds designed for selective inhibition of Golgi a-mannosidase II (GMII) exhibited varying degrees of inhibition for hLM and hEpman. While these compounds inhibited hLM and GMII similarly, they inhibited hEpman to a lesser extent. Further, the two lysosomal a-mannosidases also show differential metal dependency properties. This has led us to propose a secondary metal binding site in hEpman. These results set the stage for the development of selective inhibitors to members of the GH38 family, and, henceforth, the further investigation of their physiological roles.

Cytotechnology, 2013

The Atlantic salmon (Salmo salar) serum lectin (SSL) is a soluble C-type lectin that binds bacter... more The Atlantic salmon (Salmo salar) serum lectin (SSL) is a soluble C-type lectin that binds bacteria, including salmon pathogens. This lectin is a cysteine-rich oligomeric protein. Consequently, a Drosophila melanogaster expression system was evaluated for use in expressing SSL. A cDNA encoding SSL was cloned into a vector designed to express it as a fusion protein with a hexahistidine tag, under the control of the Drosophila methallothionein promoter. The resulting construct was stably transfected into Drosophila S2 cells. After CdCl2 induction, transfected S2 cells secreted recombinant SSL into the cell culture medium. A cell line derived from stably transformed polyclonal cell populations expressing SSL was used for large-scale expression of SSL. Recombinant SSL was purified from the culture medium using a two-step purification scheme involving affinity binding to yeast cells and metal-affinity chromatography. Although yields of SSL were very low, correct folding and functionality of the recombinant SSL purified in this manner was demonstrated by its ability to bind to Aeromonas salmonicida. Therefore, Drosophila S2 cells may be an ideal system for the production of SSL if yields can be increased.

Analytical Biochemistry, 2010

A simple and reliable continuous assay for measurement of α-mannosidase activity is described and... more A simple and reliable continuous assay for measurement of α-mannosidase activity is described and demonstrated for analysis with two recombinant human enzymes using the new substrate resorufin α-D-mannopyranoside (Res-Man). The product of enzyme reaction, resorufin, exhibits fluorescence emission at 585 nm with excitation at 571 nm and has a pKa of 5.8, allowing continuous measurement of fluorescence turnover at or near physiological pH values for human lysosomal and Drosophila Golgi α-mannosidases. The assay performed using recombinant Drosophila Golgi α-mannosidase (dGMII) has been shown to give the kinetic parameters K m of 200 μM and V max of 11 nmol/min per nmol dGMII. Methods for performing the assay using several concentrations of the known αmannosidase inhibitor swainsonine are also presented, demonstrating a potential for use of the assay as a simple method for high-throughput screening of inhibitors potentially useful in cancer treatment.

Biochemistry, 2005

Cytokinesis is the process by which one cell divides into two. Key in the cytokinetic mechanism o... more Cytokinesis is the process by which one cell divides into two. Key in the cytokinetic mechanism of Schizosaccharomyces pombe is the contractile ring myosin, which consists of two heavy chains (Myo2p), two essential light chains (Cdc4p), and two regulatory light chains (Rlc1p). Cdc4p is a dumbbell-shaped EF-hand protein composed of N- and C-terminal domains separated by a flexible linker. The properties of these two domains are of particular interest because each is hypothesized to have independent functions in binding different components of the cytokinesis machinery. To help define these properties, we used NMR spectroscopy to compare the structure, stability, and dynamics of the isolated N- and C-terminal domains with one another and with native Cdc4p. On the basis of invariant chemical shifts, the N-domain retains the same structure in isolation as in the context of the full-length Cdc4p, whereas the C-domain appears markedly perturbed. This perturbation results from intramolecular binding of the residual linker sequence at the N-terminus of the C-domain in a mode similar to that used by native Cdc4p to associate with target polypeptide sequences. NMR relaxation, thermal denaturation, and amide hydrogen exchange experiments also indicate that the C-domain is less stable and more dynamic than the N-domain, both in isolation and in the full-length protein. We hypothesize that these properties reflect a conformational plasticity of the C-domain, which may allow Cdc4p to interact with several regulatory or contractile ring proteins necessary for cytokinesis.