PLC-gamma1 signaling pathway and villin activation are involved in actin cytoskeleton reorganization induced by Na+/Pi cotransport up-regulation.
BACKGROUND
The brief incubation of opossum kidney (OK) cells with low P(i) results in Na+/P(i) cotransport up-regulation and in substantial, but transient, cytoskeletal reorganization. In this study, we examined signaling events involved in the depolymerization of microfilaments.


RESULTS
Confocal laser scanning microscopy, immunoblot and immunoprecipitation experiments revealed villin co-localization with mainly actin short filaments and monomers, indicating that under the conditions used, villin acted as an actin-severing protein. Further analysis revealed that low concentrations of extracellular phosphate resulted in phospholipase Cgammal (PLC-gammal) translocation to the actin cytoskeleton, without increases in its tyrosine phosphorylation. Additionally, tyrosine phosphorylation of a portion of insoluble villin was increased; whereas, only tyrosine phosphorylated villin associated with PLC-gammal. Although, tyrosine phosphorylation of PLC-gammal was not observed during Na+/P(i) cotransport up-regulation, genistein treatment abolished the enzyme's translocation to the actin cytoskeleton, as well as its association with villin. In addition, villin was found to associate with the 85-KDa subunit (p85) of phosphatidylinositol (PI)-3 kinase, concomitant with PLC-gammal, in the cytoskeletal fraction of Na+/P(i) cotransport up-regulated cells.


CONCLUSIONS
Our observations suggest a signaling mechanism linking low ambient P(i) levels to the acute up-regulation of its cotransport with sodium and the depolymerization of the subcortical actin cytoskeleton.
Papakonstanti
E A
EA
Department of Biochemistry, University of Crete, School of Medicine, Heraklion, Greece.
Emmanouel
D S
DS
Gravanis
A
A
Stournaras
C
C
D008841:Actin Cytoskeleton / Q000187:drug effects / Q000378:metabolism; D000199:Actins / Q000378:metabolism*; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002352:Carrier Proteins / Q000378:metabolism*; D002460:Cell Line; D003599:Cytoskeleton / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects; D019833:Genistein / Q000494:pharmacology; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000378:metabolism*; D008840:Microfilament Proteins / Q000378:metabolism*; D018613:Microscopy, Confocal; D009893:Opossums; D010710:Phosphates / Q000378:metabolism / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D051966:Phospholipase C gamma; D010766:Phosphorylation / Q000187:drug effects; D019000:Phosphotyrosine / Q000037:antagonists & inhibitors / Q000378:metabolism; D011485:Protein Binding / Q000187:drug effects; D015398:Signal Transduction / Q000187:drug effects; D012964:Sodium / Q000378:metabolism; D050608:Sodium-Phosphate Cotransporter Proteins; D012995:Solubility; D027981:Symporters; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D015854:Up-Regulation / Q000187:drug effects
D000199:Actins; D002352:Carrier Proteins; D007527:Isoenzymes; D008840:Microfilament Proteins; D010710:Phosphates; D050608:Sodium-Phosphate Cotransporter Proteins; D027981:Symporters; C026615:villin; D019000:Phosphotyrosine; D012964:Sodium; D019833:Genistein; D019869:Phosphatidylinositol 3-Kinases; D010738:Type C Phospholipases; D051966:Phospholipase C gamma