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Vasopressin Activates Akt1 Through PI‐3K in Rat Inner Medullary Collecting Duct (IMCD)
Author(s) -
Pisitkun Trairak,
Jacob Vinitha,
Yu MingJiun,
Chou ChungLin,
Knepper Mark A
Publication year - 2008
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.22.1_supplement.935.7
Subject(s) - phosphorylation , vasopressin , aquaporin 2 , calmodulin , chemistry , medicine , microbiology and biotechnology , ly294002 , intracellular , endocrinology , protein kinase b , biology , biochemistry , mechanical engineering , water channel , engineering , inlet , enzyme
Regulation of osmotic water permeability in the rat IMCD depends on vasopressin‐mediated control of AQP2 trafficking. Although it has been established that this regulation requires both an increase in cAMP and in Ca‐calmodulin, full details of vasopressin signaling are lacking. We investigated activation of Akt1 by vasopressin analog dDAVP in suspensions of freshly isolated rat IMCD using immunoblotting to assess changes in Akt1 phosphorylation. dDAVP significantly increased Akt1 phosphorylation at T308 and S473, which are both associated with activation of kinase activity. Maximal activation was seen 5–10 minutes after dDAVP addition. The LY294002 (PI‐3K inhibitor) markedly reduced phosphorylation at both sites and prevented the dDAVP‐induced increase. Immunolocalization of rat tissue sections revealed that the p110γ subunit of PI‐3K is associated with the basolateral plasma membrane of IMCD, while Akt1 is distributed throughout the cells. Addition of CPT‐cAMP increased phosphorylation at S473 but not at T308. The intracellular Ca chelator BAPTA‐AM and the calmodulin‐inhibitor W‐7 decreased phosphorylation at both sites. Use of an Akt substrate specific antibody for 2‐D immunoblotting of rat IMCD revealed several spots that changed in abundance or shifted in pI in response to dDAVP. We conclude that PI‐3K dependent Akt1 activation is part of the overall vasopressin signaling response in the rat IMCD.