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Cab39 modulates SPAK/OSR1 activation of NKCC1
Author(s) -
PonceCoria José,
Rios Kerri,
Gag Kenneth B.,
Delpire Eric
Publication year - 2013
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.27.1_supplement.732.4
Subject(s) - phosphorylation , kinase , serine , microbiology and biotechnology , chemistry , biochemistry , alanine , protein kinase a , protein serine threonine kinases , gene isoform , biology , amino acid , gene
Calcium binding protein 39 (Cab39) is a scaffolding protein that stabilizes a heterotrimeric protein complex that modulates the activity of the adenosine mono‐phosphate kinase which regulates cellular energy homeostasis. Cab39 also modulates SPAK (Ste20 related Proline Alanine rich Kinase) and OSR1 (Oxidative stress responsive kinase 1), two kinases involved in activating the Na‐K‐2Cl cotransporter‐1 (NKCC1). In this study, we demonstrate that mouse Cab39 can substitute for WNK4 phosphorylation of a key serine residue (S383) in the SPAK‐T243E mutant, and even substitute for WNK4 phosphorylation of another key activating residue (threonine 243) when two wild‐type SPAK molecules are tethered together. Western blot analysis of frog oocyte lysates shows an intense signal for an endogenous Cab39. This observation raises the question of why the mouse isoform is necessary to observe the Cab39 effect on SPAK/OSR1 activation of NKCC1. To address this problem, we cloned the cDNA encoding the Xenopus Cab39 isoform and tested its effect on SPAK/OSR1 activation of NKCC1 in frog oocytes. Using site‐directed mutagenesis, we further examined residues that might be involved in the Cab39‐SPAK‐NKCC1 regulatory pathway.