Inactivation of the calcium sensing receptor inhibits E-cadherin-mediated cell-cell adhesion and calcium-induced differentiation in human epidermal keratinocytes.
Extracellular Ca(2+) (Ca(2+)(o)) is a critical regulator that promotes differentiation in epidermal keratinocytes. The calcium sensing receptor (CaR) is essential for mediating Ca(2+) signaling during Ca(2+)(o)-induced differentiation. Inactivation of the endogenous CaR-encoding gene CASR by adenoviral expression of a CaR antisense cDNA inhibited the Ca(2+)(o)-induced increase in intracellular free calcium (Ca(2+)(i)) and expression of terminal differentiation genes, while promoting apoptosis. Ca(2+)(o) also instigates E-cadherin-mediated cell-cell adhesion, which plays a critical role in orchestrating cellular signals mediating cell survival and differentiation. Raising Ca(2+)(o) concentration ([Ca(2+)](o)) from 0.03 to 2 mm rapidly induced the co-localization of alpha-, beta-, and p120-catenin with E-cadherin in the intercellular adherens junctions (AJs). To assess whether CaR is required for the Ca(2+)(o)-induced activation of E-cadherin signaling, we examined the impact of CaR inactivation on AJ formation. Decreased CaR expression suppressed the Ca(2+)(o)-induced AJ formation, membrane translocation, and the complex formation of E-cadherin, catenins, and the phosphatidylinositol 3-kinase (PI3K), although the expression of these proteins was not affected. The assembly of the E-cadherin-catenin-PI3K complex was sensitive to the pharmacologic inhibition of Src family tyrosine kinases but was not affected by inhibition of Ca(2+)(o)-induced rise in Ca(2+)(i). Inhibition of CaR expression blocked the Ca(2+)(o)-induced tyrosine phosphorylation of beta-, gamma-, and p120-catenin, PI3K, and the tyrosine kinase Fyn and the association of Fyn with E-cadherin and PI3K. Our results indicate that the CaR regulates cell survival and Ca(2+)(o)-induced differentiation in keratinocytes at least in part by activating the E-cadherin/PI3K pathway through a Src family tyrosine kinase-mediated signaling.
Tu
Chia-Ling
CL
Endocrine Unit, Veteran Affairs Medical Center, University of California, San Francisco, California 94121; University of California, San Francisco, California 94121. Electronic address: chia-ling.tu@ucsf.edu.
Chang
Wenhan
W
Endocrine Unit, Veteran Affairs Medical Center, University of California, San Francisco, California 94121; University of California, San Francisco, California 94121.
Xie
Zhongjian
Z
Endocrine Unit, Veteran Affairs Medical Center, University of California, San Francisco, California 94121; Northern California Institute for Research and Education, University of California, San Francisco, California 94121.
Bikle
Daniel D
DD
Endocrine Unit, Veteran Affairs Medical Center, University of California, San Francisco, California 94121; University of California, San Francisco, California 94121.
D017209:Apoptosis; D015820:Cadherins / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D002448:Cell Adhesion; D002454:Cell Differentiation; D002478:Cells, Cultured; D018076:DNA, Complementary / Q000378:metabolism; D004817:Epidermis / Q000378:metabolism*; D006801:Humans; D020287:In Situ Nick-End Labeling; D015603:Keratinocytes / Q000378:metabolism*; D008954:Models, Biological; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation; D044169:Receptors, Calcium-Sensing / Q000037:antagonists & inhibitors* / Q000378:metabolism*
D015820:Cadherins; D018076:DNA, Complementary; D044169:Receptors, Calcium-Sensing; D019869:Phosphatidylinositol 3-Kinases; D002118:Calcium