Epidermal growth factor activates Na(+/)H(+) exchanger in podocytes through a mechanism that involves Janus kinase and calmodulin. Biochim Biophys Acta 2009 Jul;1793(7):1174-81
Date
04/04/2009Pubmed ID
19341767Pubmed Central ID
PMC3364543DOI
10.1016/j.bbamcr.2009.03.006Scopus ID
2-s2.0-67649390829 (requires institutional sign-in at Scopus site) 45 CitationsAbstract
Sodium-proton exchanger type 1 (NHE-1) is ubiquitously expressed, is activated by numerous growth factors, and plays significant roles in regulating intracellular pH and cellular volume, proliferation and cytoskeleton. Despite its importance, little is known about its regulation in renal glomerular podocytes. In the current work, we studied the regulation of NHE-1 activity by the epidermal growth factor receptor (EGFR) in cultured podocytes. RT-PCR demonstrated mRNAs for NHE-1 and NHE-2 in differentiated podocytes, as well as for EGFR subunits EGFR/ErbB1, Erb3, and ErbB4. EGF induced concentration-dependent increases in proton efflux in renal podocytes as assessed using a Cytosensor microphysiometer, were diminished in the presence of 5-(N-methyl-N-isobutyl) amiloride or in a sodium-free solution. Furthermore, pharmacological inhibitors of Janus kinase (Jak2) and calmodulin (CaM) attenuated EGF-induced NHE-1 activity. Co-immunoprecipitation studies determined that EGF induced formation of complexes between Jak2 and CaM, as well as between CaM and NHE-1. In addition, EGF increased levels of tyrosine phosphorylation of Jak2 and CaM. The EGFR kinase inhibitor, AG1478, blocked activation of NHE-1, but did not block EGF-induced phosphorylation of Jak2 or CaM. These results suggest that EGF induces NHE-1 activity in podocytes through two pathways: (1) EGF-->EGFR-->Jak2 activation (independent of EGFR tyrosine kinase activity)-->tyrosine phosphorylation of CaM-->CaM binding to NHE-1-->conformational change of NHE-1-->activation of NHE-1; and (2) EGF-->EGFR-->EGFR kinase activation-->association of CaM with NHE-1 (independent of Jak2)-->conformational change of NHE-1-->activation of NHE-1.
Author List
Coaxum SD, Garnovskaya MN, Gooz M, Baldys A, Raymond JRAuthor
John R. Raymond MD President, CEO, Professor in the President department at Medical College of WisconsinMESH terms used to index this publication - Major topics in bold
Blotting, WesternCalmodulin
Cell Differentiation
Cells, Cultured
Epidermal Growth Factor
ErbB Receptors
Fluorescent Antibody Technique
Humans
Immunoenzyme Techniques
Immunoprecipitation
Janus Kinases
Luciferases
Phosphorylation
Podocytes
RNA, Messenger
Receptor, ErbB-4
Reverse Transcriptase Polymerase Chain Reaction
Sodium-Hydrogen Exchangers
Transfection