关键词： PHOSPHOLIPASE-C-EPSILON   FOCAL SEGMENTAL GLOMERULOSCLEROSIS   MESANGIALSCLEROSIS   PODOCYTE DEPLETION   GLOMERULAR PROTEIN   DRASH-SYNDROME   NEPHRIN   PODOCALYXIN   EXPRESSION   IQGAP1  

摘要： Nephrotic syndrome, a malfunction of the kidney glomerular filter, leads to proteinuria, edema and, in steroid-resistant nephrotic syndrome, end-stage kidney disease. Using positional cloning, we identified mutations in the phospholipase C epsilon gene (PLCE1) as causing early-onset nephrotic syndrome with end-stage kidney disease. Kidney histology of affected individuals showed diffuse mesangial sclerosis (DMS). Using immunofluorescence, we found PLC epsilon 1 expression in developing and mature glomerular podocytes and showed that DMS represents an arrest of normal glomerular development. We identified IQ motif-containing GTPase-activating protein 1 as a new interaction partner of PLC epsilon 1. Two siblings with a missense mutation in an exon encoding the PLCe1 catalytic domain showed histology characteristic of focal segmental glomerulosclerosis. Notably, two other affected individuals responded to therapy, making this the first report of a molecular cause of nephrotic syndrome that may resolve after therapy. These findings, together with the zebrafish model of human nephrotic syndrome generated by plce1 knockdown, open new inroads into pathophysiology and treatment mechanisms of nephrotic syndrome.

关键词： Adult neurogenesis   Neural progenitors   IQGAP1   VEGF   Migration  

关键词： IQGAP1   ovarian carcinoma   cell adhesion   cytoskeleton   tumor invasion   metastasis  

摘要： IQGAP1 is a multifunctional protein involved in actin cytoskeleton assembly and E-cadherin-mediated cell adhesion. To determine the role of IQGAP1 in ovarian tumors, we evaluated IQGAP1 expression by immunohistochemistry in 17 adenomas, 30 borderline tumors and 80 adenocarcinomas and its relation with patient survival. IQGAP1 was overexpressed in adenocarcinomas compared with adenomas and borderline tumors. Enhanced immunostaining in invasive tumor fronts was categorized as focal or diffuse. The diffuse expression pattern correlated with high histological grade and clinicopathological stages. IQGAP1 overexpression and diffuse invasion pattern were significantly associated with poor prognosis by multivariate analysis. Our findings suggest the involvement of IQGAP1 in the progression and spread of ovarian adenocarcinomas. Overexpression and diffuse expression pattern of IQGAP1 are potentially useful independent molecular predictors of highly aggressive ovarian carcinomas. (c) 2005 Elsevier Ireland Ltd. All rights reserved.

关键词： calmodulin-dependent protein kinase II   Antigens   CD29   Integrins   EpidermalGrowth Factor  

摘要： Maintenance of 01 integrin-mediated cell adhesion in quiescent human mammary epithelial (HME) cells requires protein phosphatase (PP) 2A for not only dephosphorylation of beta 1 integrin but also recruitment of IQGAP1 to Rac-bound beta 1 integrin. However, how PP2A-dependent regulatory machinery of cell adhesion responds to EGF remains to be elucidated. We report here that phosphorylated Ca2+/calmodulin-dependent protein kinase II(CaMKII) at threonine 286 was involved in the beta 1 integrin complex that consisted of PP2A, Rac, and IQGAP1 in quiescent HME cells. Stimulation of the cells with EGF concomitantly induced an increase in intracellular Ca2+, activation of CaMKII, and dissociation of PP2A-IQGAP1-CaMKII from beta 1 integrin-Rac. Because the activation of CaMKII and dissociation of PP2A-IQGAP1-CaMKII were blocked by either Ca2+-chelator or CaMKII inhibitor, we therefore propose that EGF has the ability to abrogate the PP2A function in the maintenance of P1 integrin-mediated cell adhesion by dissociation of PP2A-IQGAP1-CaMKII from beta 1 integrin-Rac through activation of CaMKII.

关键词： Proteomics   Actins   Bile Canaliculi   Biopsy   Cell Polarity   Cells   Cultured   Cytoskeletal Proteins   Cytoskeleton   Gallium   Hepatocytes   Humans   Intercellular Junctions   Liver   Liver Transplantation   Polymers   Reperfusion Injury   Tissue Distribution   Transfection   Zinc   ras GTPase-Activating Proteins  

摘要： Ischemia-reperfusion injury (IRI) represents a major determinant of liver transplantation. IRI-induced graft dysfunction is related to biliary damage, partly due to a loss of bile canaliculi (BC) integrity associated with a dramatic remodeling of actin cytoskeleton. However, the molecular mechanisms associated with these events remain poorly characterized. Using liver biopsies collected during the early phases of organ procurement (ischemia) and transplantation (reperfusion), we characterized the global patterns of expression and phosphorylation of cytoskeleton-related proteins during hepatic IRI. This targeted functional proteomic approach, which combined protein expression pattern profiling and phosphoprotein enrichment followed by mass spectrometry analysis, allowed us to identify IQGAP1, a Cdc42/Rac1 effector, as a potential regulator of actin cytoskeleton remodeling and maintenance of BC integrity. Cell fractionation and immunohistochemistry revealed that IQGAP1 expression and localization were affected upon IRI and related to actin reorganization. Furthermore using an IRI model in human hepatoma cells, we demonstrated that IQGAP1 silencing decreased the basal level of actin polymerization at BC periphery, reflecting a defect in BC structure coincident with reduced cellular resistance to IRI. In summary, this study uncovered new mechanistic insights into the global regulation of IRI-induced cytoskeleton remodeling and led to the identification of IQGAP1 as a regulator of BC structure. IQGAP1 therefore represents a potential target for the design of new organ preservation strategies to improve transplantation outcome.

关键词： GTPASE-activating protein   PROTEINS   CELL physiology   ACTIN   PROTEIN kinases   CELLULAR growth  

摘要： IQGAP1 was identified in 1994 as a widely expressed IQ domain-containing protein with a region containing sequence similarity to the Ras GTPase-activating proteins. IQGAP1 has roles in many different aspects of cell physiology and interacts with numerous proteins. It modulates the actin cytoskeleton through Rac1 and Cdc42, and cell-cell adhesion through E-cadherin and beta-catenin. It also regulates the mitogen activated protein kinase pathway, which influences cell proliferation and differentiation. Evidence suggests that IQGAP1 is a scaffold protein that links components of signaling cascades. Here, we evaluate recent data that identify the participation of IQGAP1 in signaling networks and we illustrate how this influences diverse cellular functions. These findings suggest that IQGAP1 integrates signaling pathways and coordinates several fundamental cellular activities.

关键词： Cadherins   Cells   Cell Adhesion   Phosphoprotein Phosphatase  

摘要： Serine/threonine protein phosphatase (PP) 2A regulates many biological processes, however it remains unclear whether PP2A participates in cadherin-mediated cell-cell adhesion. We show here that the core enzyme of PP2A (PP2A-AC) is localized in the cell-cell adhesion sites between adjacent cells and associated with the E-cadherin-catenins complex in non-malignant human mammary epithelial (HME) cells at confluence. Treatment of the cells with either okadaic acid (OA), an inhibitor of PP2A, or siRNA for the regulatory subunit A of PP2A (PP2A-A) caused disruption of cell-cell adhesion and F-actin assembly, without affecting the complex formation of E-cadherin with beta- and alpha-catenins. While a small GTPase Rac and its effector IQGAP1 were associated with the E-cadherin-catenins complex, either OA or PP2A-A siRNA concomitantly induced the dissociation of IQGAP1, but not Rac, from the complex and the internalization of E-cadherin from the cell surface. We, therefore, propose that PP2A plays a crucial role in the maintenance of cell-cell adhesion through recruitment of IQGAP1 to the Rac-bound E-cadherin-catenins complex. (C) 2005 Wiley-Liss, Inc.

关键词： Gene Expression Regulation   Neoplastic   Protein-Tyrosine-Phosphatase   rasGTPase-Activating Proteins  

摘要： The receptor protein-tyrosine phosphatase PTP mu is a member of the Ig superfamily of cell adhesion molecules. The extracellular domain of PTP mu contains motifs commonly found in cell adhesion molecules. The intracellular domain of PTP mu contains two conserved catalytic domains, only the membrane-proximal domain has catalytic activity. The unique features of PTP mu make it an attractive molecule to transduce signals upon cell-cell contact. PTP mu has been shown to regulate cadherin-mediated cell adhesion, neurite outgrowth, and axon guidance. Protein kinase C is a component of the PTP mu signaling pathway utilized to regulate these events. To aid in the further characterization of PTP mu signaling pathways, we used a series of GST-PTP mu fusion proteins, including catalytically inactive and substrate trapping mutants, to identify PTP mu-interacting proteins. We identified IQGAP1, a known regulator of the Rho GTPases, Cdc42 and Rac1, as a novel PTP mu-interacting protein. We show that this interaction is due to direct binding. In addition, we demonstrate that amino acid residues 765-958 of PTP mu, which include the juxtamembrane domain and 35 residues of the first phosphatase domain, mediate the binding to IQGAP1. Furthermore, we demonstrate that constitutively active Cdc42, and to a lesser extent Rac1, enhances the interaction of PTP mu and IQGAP1. These data indicate PTP mu may regulate Rho-GTPase-dependent functions of IQGAP1 and suggest that IQGAP1 is a component of the PTP mu signaling pathway. In support of this, we show that a peptide that competes IQGAP1 binding to Rho GTPases blocks PTP mu-mediated neurite outgrowth.

关键词： Calcium   Cell Movement   Microtubule-Associated Proteins   Neurons   cdc42GTP-Binding Protein  

摘要： Lis1 gene defects impair neuronal migration, causing the severe human brain malformation lissencephaly. Although much is known about its interactions with microtubules, microtubule-binding proteins such as CLIP-170, and with the dynein motor complex, the response of Lis1 to neuronal motility signals has not been elucidated. Lis1 deficiency is associated with deregulation of the Rho-family GTPases Cdc42, Rac1 and RhoA, and ensuing actin cytoskeletal defects, but the link between Lis1 and Rho GTPases remains unclear. We report here that calcium influx enhances neuronal motility through Lis1-dependent regulation of Rho GTPases. Lis1 promotes Cdc42 activation through interaction with the calcium sensitive GTPase scaffolding protein IQGAP1, maintaining the perimembrane localization of IQGAP1 and CLIP170 and thereby tethering microtubule ends to the cortical actin cytoskeleton. Lis1 thus is a key component of neuronal motility signal transduction that regulates the cytoskeleton by complexing with IQGAP1, active Cdc42 and CLIP-170 upon calcium influx.