Fenny Wiradjaja - Academia.edu (original) (raw)

Papers by Fenny Wiradjaja

The International Journal of Biochemistry & Cell Biology, 2005

Phosphoinositides are membrane-bound signaling molecules that recruit, activate and localize targ... more Phosphoinositides are membrane-bound signaling molecules that recruit, activate and localize target effectors to intracellular membranes regulating apoptosis, cell proliferation, insulin signaling and membrane trafficking. The SH2 domain containing inositol polyphosphate 5-phosphatase-2 (SHIP2) hydrolyzes phosphatidylinositol 3,4,5-trisphosphate (PtdIns(3,4,5)P3) generating phosphatidylinositol 3,4-bisphosphate (PtdIns(3,4)P2). Overexpression of SHIP2 inhibits insulin-stimulated phosphoinositide 3-kinase (PI3K) dependent signaling events. Analysis of diabetic human subjects has revealed an association between SHIP2 gene polymorphisms and type 2 diabetes mellitus. Genetic ablation of SHIP2 in mice has generated conflicting results. SHIP2 knockout mice were originally reported to show lethal neonatal hypoglycemia resulting from insulin hypersensitivity, but in addition to inactivating the SHIP2 gene, the Phox2a gene was also inadvertently deleted. Another SHIP2 knockout mouse has now been generated which inactivates the SHIP2 gene but leaves Phox2a intact. These animals show normal insulin and glucose tolerance but are highly resistant to weight gain on high fat diets, exhibiting an obesity-resistant phenotype. Therefore, SHIP2 remains a significant therapeutic target for the treatment of both obesity and type 2 diabetes.

Molecular and Cellular Biology, 2000

The Saccharomyces cerevisiae inositol polyphosphate 5-phosphatases (Inp51p, Inp52p, and Inp53p) e... more The Saccharomyces cerevisiae inositol polyphosphate 5-phosphatases (Inp51p, Inp52p, and Inp53p) each contain an N-terminal Sac1 domain, followed by a 5-phosphatase domain and a C-terminal proline-rich domain. Disruption of any two of these 5-phosphatases results in abnormal vacuolar and plasma membrane morphology. We have cloned and characterized the Sac1-containing 5-phosphatases Inp52p and Inp53p. Purified recombinant Inp52p lacking the Sac1 domain hydrolyzed phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2] and PtdIns(3,5)P2. Inp52p and Inp53p were expressed in yeast as N-terminal fusion proteins with green fluorescent protein (GFP). In resting cells recombinant GFP-tagged 5-phosphatases were expressed diffusely throughout the cell but were excluded from the nucleus. Following hyperosmotic stress the GFP-tagged 5-phosphatases rapidly and transiently associated with actin patches, independent of actin, in both the mother and daughter cells of budding yeast as demonstrated by c...

Journal of Biological Chemistry, 2001

The budding yeast Saccharomyces cerevisiae has four inositol polyphosphate 5-phosphatase (5-phosp... more The budding yeast Saccharomyces cerevisiae has four inositol polyphosphate 5-phosphatase (5-phosphatase) genes, INP51, INP52, INP53, and INP54, all of which hydrolyze phosphatidylinositol (4,5)-bisphosphate. INP54 encodes a protein of 44 kDa which consists of a 5-phosphatase domain and a C-terminal leucine-rich tail, but lacks the N-terminal SacI domain and proline-rich region found in the other three yeast 5-phosphatases. We report that Inp54p belongs to the family of tail-anchored proteins and is localized to the endoplasmic reticulum via a C-terminal hydrophobic tail. The hydrophobic tail comprises the last 13 amino acids of the protein and is sufficient to target green fluorescent protein to the endoplasmic reticulum. Protease protection assays demonstrated that the N terminus of Inp54p is oriented toward the cytoplasm of the cell, with the C terminus of the protein also exposed to the cytosol. Null mutation of INP54 resulted in a 2-fold increase in secretion of a reporter protein, compared with wild-type yeast or cells deleted for any of the SacI domain-containing 5-phosphatases. We propose that Inp54p plays a role in regulating secretion, possibly by modulating the levels of phosphatidylinositol (4,5)-bisphosphate on the cytoplasmic surface of the endoplasmic reticulum membrane.

Journal of Biological Chemistry, 2007

Phosphoinositides direct membrane trafficking, facilitating the recruitment of effectors to speci... more Phosphoinositides direct membrane trafficking, facilitating the recruitment of effectors to specific membranes. In yeast phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P 2 ) is proposed to regulate vacuolar fusion; however, in intact cells this phosphoinositide can only be detected at the plasma membrane. In Saccharomyces cerevisiae the 5-phosphatase, Inp54p, dephosphorylates PtdIns(4,5)P 2 forming PtdIns(4)P, a substrate for the phosphatase Sac1p, which hydrolyzes (PtdIns(4)P). We investigated the role these phosphatases in regulating PtdIns(4,5)P 2 subcellular distribution. PtdIns(4,5)P 2 bioprobes exhibited loss of plasma membrane localization and instead labeled a subset of fragmented vacuoles in ⌬sac1 ⌬inp54 and sac1 ts ⌬inp54 mutants. Furthermore, sac1 ts ⌬inp54 mutants exhibited vacuolar fusion defects, which were rescued by latrunculin A treatment, or by inactivation of Mss4p, a PtdIns(4)P 5-kinase that synthesizes plasma membrane PtdIns(4,5)P 2 . Under these conditions PtdIns(4,5)P 2 was not detected on vacuole membranes, and vacuole morphology was normal, indicating vacuolar PtdIns(4,5)P 2 derives from Mss4p-generated plasma membrane PtdIns(4,5)P 2 . ⌬sac1 ⌬inp54 mutants exhibited delayed carboxypeptidase Y sorting, cargo-selective secretion defects, and defects in vacuole function. These studies reveal PtdIns(4,5)P 2 hydrolysis by lipid phosphatases governs its spatial distribution, and loss of phosphatase activity may result in PtdIns(4,5)P 2 accumulation on vacuole membranes leading to vacuolar fragmentation/fusion defects.

IUBMB Life, 2007

The Fras1 and Frem extracellular matrix proteins play critical roles in epithelial-mesenchymal in... more The Fras1 and Frem extracellular matrix proteins play critical roles in epithelial-mesenchymal interaction during embryonic development. Loss of function in humans results in a recessive embryonic blistering disorder called Fraser syndrome. Inactivation of these proteins, or the proteins with which they interact (e.g., Grip1) has also been shown to underlie members of the 'bleb' family of classic mouse mutants which provide a valuable model of Fraser syndrome. Recent studies supporting direct interactions between the Fras1 and Frem proteins, combined with more rigorous elucidation of their developmental regulation, have shed new light on their activity. We summarize the findings to date, bringing new insight into their role in the regulation of epidermal-basement membrane adhesion and organogenesis during development.

IUBMB Life (International Union of Biochemistry and Molecular Biology: Life), 2002

Phosphoinositide signaling pathways regulate many essential cellular functions including prolifer... more Phosphoinositide signaling pathways regulate many essential cellular functions including proliferation, differentiation and survival, cytoskeletal organization, and vesicular trafficking. The inositol polyphosphate 5-phosphatases regulate the cellular levels of several bioactive phosphoinositide species. This review describes the structure and function of the 5-phosphatase and Sac1 catalytic domains of these enzymes. The crystal structure of the 5-phosphatase domain has been solved and shares homology with members of the AP endonuclease family. The phosphoinositide polyphosphatase activity of the Sac1 domain, found in some inositol polyphosphate 5-phosphatases, is defined by a motif, CX 5 R(T/S), also found in both protein and lipid phosphatases. IUBMB Life, 53: 15-23, 2002 1 Abbreviations: PtdIns, phosphatidylinositol; SHIP, src homology-2containing inositol 5-phosphatase; OCRL, oculocerebrorenal syndrome of Lowe; INP51-4, inositol polyphosphate 5-phosphatase 1-4; AP endonuclease, Apurinic/Apyrimidinic base excision repair endonuclease; Sac1, suppressor of actin-1; Fig4, factor-induced gene 4.

The Journal of biological chemistry, Jan 26, 2011

Phosphoinositide 3-kinase (PI3K) regulates cell polarity and migration by generating phosphatidyl... more Phosphoinositide 3-kinase (PI3K) regulates cell polarity and migration by generating phosphatidylinositol 3,4,5-trisphosphate (PI(3,4,5)P(3)) at the leading edge of migrating cells. The serine-threonine protein kinase Akt binds to PI(3,4,5)P(3), resulting in its activation. Active Akt promotes spatially regulated actin cytoskeletal remodeling and thereby directed cell migration. The inositol polyphosphate 5-phosphatases (5-ptases) degrade PI(3,4,5)P(3) to form PI(3,4)P(2), which leads to diminished Akt activation. Several 5-ptases, including SKIP and SHIP2, inhibit actin cytoskeletal reorganization by opposing PI3K/Akt signaling. In this current study, we identify a molecular co-chaperone termed silencer of death domains (SODD/BAG4) that forms a complex with several 5-ptase family members, including SKIP, SHIP1, and SHIP2. The interaction between SODD and SKIP exerts an inhibitory effect on SKIP PI(3,4,5)P(3) 5-ptase catalytic activity and consequently enhances the recruitment of PI...

Birth Defects Research Part C: Embryo Today: Reviews, 2010

Basement membranes (BMs) are specializations of the extracellular matrix that act as key mediator... more Basement membranes (BMs) are specializations of the extracellular matrix that act as key mediators of development and disease. Their sheet like protein matrices typically serve to separate epithelial or endothelial cell layers from underlying mesenchymal tissues, providing both a biophysical support to overlying tissue as well as a hub to promote and regulate cell-cell and cell-protein interactions. In the latter context, the BM is increasingly being recognized as a mediator of growth factor interactions during development. In this review, we discuss recent findings regarding the structure of the BM and its roles in mediating the normal development of the embryo, and we examine congenital diseases affecting the BM which impact embryonic development and health in later life.

Fras1-related extracellular matrix protein 1 (FREM1) is required for epidermal adhesion during em... more Fras1-related extracellular matrix protein 1 (FREM1) is required for epidermal adhesion during embryogenesis, and mice lacking the gene develop fetal skin blisters and a range of other developmental defects. Mutations in members of the FRAS/FREM gene family cause diseases of the Fraser syndrome spectrum. Embryonic epidermal blistering is also observed in mice lacking PdgfC and its receptor, PDGFRα. In this article, we show that FREM1 binds to PDGFC and that this interaction regulates signalling downstream of PDGFRα. Fibroblasts from Frem1-mutant mice respond to PDGFC stimulation, but with a shorter duration and amplitude than do wild-type cells. Significantly, PDGFC-stimulated expression of the metalloproteinase inhibitor Timp1 is reduced in cells with Frem1 mutations, leading to reduced basement membrane collagen I deposition. These results show that the physical interaction of FREM1 with PDGFC can regulate remodelling of the extracellular matrix downstream of PDGFRα. We propose that loss of FREM1 function promotes epidermal blistering in Fraser syndrome as a consequence of reduced PDGFC activity, in addition to its stabilising role in the basement membrane.

PLoS Genetics, 2011

The premature fusion of the paired frontal bones results in metopic craniosynostosis (MC) and giv... more The premature fusion of the paired frontal bones results in metopic craniosynostosis (MC) and gives rise to the clinical phenotype of trigonocephaly. Deletions of chromosome 9p22.3 are well described as a cause of MC with variably penetrant midface hypoplasia. In order to identify the gene responsible for the trigonocephaly component of the 9p22.3 syndrome, a cohort of 109 patients were assessed by high-resolution arrays and MLPA for copy number variations (CNVs) involving 9p22. Five CNVs involving FREM1, all of which were de novo variants, were identified by array-based analyses. The remaining 104 patients with MC were then subjected to targeted FREM1 gene re-sequencing, which identified 3 further mutant alleles, one of which was de novo. Consistent with a pathogenic role, mouse Frem1 mRNA and protein expression was demonstrated in the metopic suture as well as in the pericranium and dura mater. Micro-computed tomography based analyses of the mouse posterior frontal (PF) suture, the human metopic suture equivalent, revealed advanced fusion in all mice homozygous for either of two different Frem1 mutant alleles, while heterozygotes exhibited variably penetrant PF suture anomalies. Gene dosage-related penetrance of midfacial hypoplasia was also evident in the Frem1 mutants. These data suggest that CNVs and mutations involving FREM1 can be identified in a significant percentage of people with MC with or without midface hypoplasia. Furthermore, we present Frem1 mutant mice as the first bona fide mouse model of human metopic craniosynostosis and a new model for midfacial hypoplasia.