CFTR Cl– channel functional regulation by phosphorylation of focal adhesion kinase at tyrosine 407 in osmosensitive ion transporting mitochondria rich cells of euryhaline killifish
Author:
Marshall William S.1, Watters Kaitlyn D.1, Hovdestad Leah R.1, Cozzi Regina R. F.1, Katoh Fumi1
Affiliation:
1. Department of Biology, St Francis Xavier University, PO Box 5000 Antigonish, Nova Scotia, Canada B2G 2W5
Abstract
SUMMARY
Cystic fibrosis transmembrane conductance regulator (CFTR) anion channels are the regulated exit pathway in Cl– secretion by teleost mitochondria rich salt secreting (MR) cells of the gill and opercular epithelia of euryhaline teleosts. By confocal light immunocytochemistry,immunogold transmission electron microscopy (TEM), and co-immunoprecipitation,using regular and phospho-antibodies directed against conserved sites, we found that killifish CFTR (kfCFTR) and the tyrosine kinase focal adhesion kinase (FAK) phosphorylated at Y407 (FAK pY407) are colocalized in the apical membrane and in subjacent membrane vesicles of MR cells. We showed previously that basolateral FAK pY407, unlike other FAK phosphorylation sites, is osmosensitive and dephosphorylates during hypotonic shock of epithelial cells(Marshall et al., 2008). In the present study, we found that hypotonic shock and theα 2-adrenergic agonist clonidine (neither of which affects cAMP levels) rapidly and reversibly inhibit Cl– secretion by isolated opercular membranes, simultaneous with dephosphorylation of FAK pY407, located in the apical membrane. FAK pY407 is rephosphorylated and Cl– secretion rapidly restored by hypertonic shock as well as by forskolin and isoproterenol, which operate via cAMP and protein kinase A. We conclude that hormone mediated, cAMP dependent and osmotically mediated, cAMP independent pathways converge on a mechanism to activate CFTR and Cl– secretion, possibly through tyrosine phosphorylation of CFTR by FAK.
Publisher
The Company of Biologists
Subject
Insect Science,Molecular Biology,Animal Science and Zoology,Aquatic Science,Physiology,Ecology, Evolution, Behavior and Systematics
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