MAPKinase and regulation of the sodium-proton exchanger in human red blood cell.
The sodium-proton exchanger is activated by various agonists, including insulin, even in human red blood cell. MAPKinase, a family of ubiquitous serine/threonine kinases, plays an important role in the signal transduction pathways which lead to sodium-proton exchanger activation. The aim of our study was to establish the existence of MAPKinase in human red blood cell and to investigate the effects of its activation by insulin and okadaic acid on the sodium-proton exchanger. Immunoblot with antiMAPK antibody revealed the presence of two isoforms, p44(ERK1) and p42(ERK2). Insulin stimulated MAPKinase activity and increased the phosphorylation of MAPK tyrosine residues, with a peak time between 3 and 5 min. Okadaic acid, an inhibitor of serine/threonine phosphatases, stimulated MAPKinase activity. In the presence of PD98059, an inhibitor of MEK, the upstream activator of MAPKinase, insulin and okadaic acid failed to stimulate MAPKinase. Insulin and okadaic acid increased the activity of the sodium-proton exchanger and this effect was abolished by PD98059. In conclusion, we first describe the presence and activity of MAPKinase in human red blood cell. Furthermore, we demonstrate that in human red blood cell, insulin modulates the sodium-proton exchanger through MAPKinase activation.
Sartori
M
M
Department of Clinical and Experimental Medicine, University of Padua Medical School, Padua, Italy.
Ceolotto
G
G
Semplicini
A
A
D000328:Adult; D004789:Enzyme Activation; D004912:Erythrocytes / Q000187:drug effects / Q000201:enzymology*; D005419:Flavonoids / Q000494:pharmacology; D006801:Humans; D015151:Immunoblotting; D007328:Insulin / Q000494:pharmacology; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D019319:Okadaic Acid / Q000494:pharmacology; D015398:Signal Transduction; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism*
D005419:Flavonoids; D007328:Insulin; D017923:Sodium-Hydrogen Exchangers; D019319:Okadaic Acid; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one