18 research outputs found
Type I gamma phosphatidylinositol phosphate kinase modulates invasion and proliferation and its expression correlates with poor prognosis in breast cancer
PIPKIΞ³ Regulates Focal Adhesion Dynamics and Colon Cancer Cell Invasion
Focal adhesion assembly and disassembly are essential for cell migration and cancer invasion, but the detailed molecular mechanisms regulating these processes remain to be elucidated. Phosphatidylinositol phosphate kinase type IΞ³ (PIPKIΞ³) binds talin and is required for focal adhesion formation in EGF-stimulated cells, but its role in regulating focal adhesion dynamics and cancer invasion is poorly understood. We show here that overexpression of PIPKIΞ³ promoted focal adhesion formation, whereas cells expressing either PIPKIΞ³K188,200R or PIPKIΞ³D316K, two kinase-dead mutants, had much fewer focal adhesions than those expressing WT PIPKIΞ³ in CHO-K1 cells and HCT116 colon cancer cells. Furthermore, overexpression of PIPKIΞ³, but not PIPKIΞ³K188,200R, resulted in an increase in both focal adhesion assembly and disassembly rates. Depletion of PIPKIΞ³ by using shRNA strongly inhibited formation of focal adhesions in HCT116 cells. Overexpression of PIPKIΞ³K188,200R or depletion of PIPKIΞ³ reduced the strength of HCT116 cell adhesion to fibronection and inhibited the invasive capacities of HCT116 cells. PIPKIΞ³ depletion reduced PIP2 levels to βΌ40% of control and PIP3 to undetectable levels, and inhibited vinculin localizing to focal adhesions. Taken together, PIPKIΞ³ positively regulates focal adhesion dynamics and cancer invasion, most probably through PIP2-mediated vinculin activation
Lowe Syndrome Protein OCRL1 Supports Maturation of Polarized Epithelial Cells
Mutations in the inositol polyphosphate 5-phosphatase OCRL1 cause Lowe Syndrome, leading to cataracts, mental retardation and renal failure. We noted that cell types affected in Lowe Syndrome are highly polarized, and therefore we studied OCRL1 in epithelial cells as they mature from isolated individual cells into polarized sheets and cysts with extensive communication between neighbouring cells. We show that a proportion of OCRL1 targets intercellular junctions at the early stages of their formation, co-localizing both with adherens junctional components and with tight junctional components. Correlating with this distribution, OCRL1 forms complexes with junctional components Ξ±-catenin and zonula occludens (ZO)-1/2/3. Depletion of OCRL1 in epithelial cells growing as a sheet inhibits maturation; cells remain flat, fail to polarize apical markers and also show reduced proliferation. The effect on shape is reverted by re-expressed OCRL1 and requires the 5β²-phosphatase domain, indicating that down-regulation of 5-phosphorylated inositides is necessary for epithelial development. The effect of OCRL1 in epithelial maturation is seen more strongly in 3-dimensional cultures, where epithelial cells lacking OCRL1 not only fail to form a central lumen, but also do not have the correct intracellular distribution of ZO-1, suggesting that OCRL1 functions early in the maturation of intercellular junctions when cells grow as cysts. A role of OCRL1 in junctions of polarized cells may explain the pattern of organs affected in Lowe Syndrome
Risk-Oriented Assessment Model for Project Bidding Selection in Construction Industry of Pakistan Based on Fuzzy AHP and TOPSIS Methods
Not so simple: the complexity of phosphotyrosine signaling at cadherin adhesive contacts
Cadherin cell-cell adhesion critically determines tissue organization and integrity in many organs of the body. Cadherin function influences patterning and morphogenesis while cadherin dysfunction contributes to disease, notably tumor invasion and metastasis. Cell signaling events are intimately linked with cadherin function; it is increasingly apparent that not only do cellular signals regulate cadherin function, but cadherins can also, in turn, modulate cell signaling itself. In this review, we discuss the complex interrelationship between phosphotyrosine-based cell signaling and cadherin adhesion. We focus on the interplay of events that occur at the cell surface and address three issues: the diverse mechanisms that activate phosphotyrosine signaling at cadherin cell-cell contacts, the functional impact of such signaling for cadherin adhesion, and the emerging capacity for cadherins to regulate growth factor signaling
The RhoGAP protein Deleted in Liver Cancer 3 (DLC3) is essential for adherens junctions integrity
Actin cytoskeleton remodelling in the anterior pituitary folliculostellate cell line TtT/GF: participation of the actin-binding protein cortactin
Palmitoylation of Ξ΄-catenin by DHHC5 mediates activity-induced synapse plasticity
Synaptic cadherin adhesion complexes are known to be key regulators of synapse plasticity. However, the molecular mechanisms that coordinate activity-induced modifications in cadherin localization and adhesion and subsequent changes in synapse morphology and efficacy, remain unanswered. We demonstrate that the intracellular cadherin binding protein, Ξ΄-catenin, is transiently palmitoylated by DHHC5 following enhanced synaptic activity, and that palmitoylation increases Ξ΄-catenin/cadherin interactions at synapses. Both the palmitoylation of Ξ΄-catenin and its binding to cadherin are required for activity-induced stabilization of N-cadherin at synapses, the enlargement of postsynaptic spines, as well as insertion of GluA1 and GluA2 subunits into the synaptic membrane and the concomitant increase in mEPSC amplitude. Importantly, context-dependent fear conditioning in mice results in increased Ξ΄-catenin palmitoylation as well as increased Ξ΄-catenin/cadherin associations at hippocampal synapses. Together, this suggests a role for palmitoylated Ξ΄-catenin in coordinating activity-dependent changes in synaptic adhesion molecules, synapse structure, and receptor localization that are involved in memory formation