Regulation of rat Na+-K+-ATPase activity by PKC is modulated by state of phosphorylation of Ser-943 by PKA

• Published in: American Journal of Physiology: Cell Physiology 1997-12, Vol.273 (6), p.C1981-C1986
• Main Authors: Cheng, Xian-Jun, Hoog, Jan-Olov, Nairn, Angus C, Greengard, Paul, Aperia, Anita
• Format: Article
• Language: English
• ISSN: 0363-6143; 1522-1563
• DOI: 10.1152/ajpcell.1997.273.6.c1981

Department of Woman and Child Health and Department of Medical Biochemistry and Biophysics, Karolinska Institute, S-11281 Stockholm, Sweden; and Laboratory of Molecular and Cellular Neuroscience, The Rockefeller University, New York, New York 10021 We have previously shown that the rat Na + -K + -ATPase 1 -isoform is phosphorylated at Ser-943 by protein kinase A (PKA) and at Ser-23 by protein kinase C (PKC), which in both cases results in inhibition of enzyme activity. We now present evidence that suggests that the phosphorylation of Ser-943 by PKA modulates the response of Na + -K + -ATPase to PKC. Rat Na + -K + -ATPase 1 or a mutant in which Ser-943 was changed to Ala-943 was stably expressed in COS cells. The inhibition of enzyme activity measured in response to treatment with the phorbol ester, phorbol 12,13-dibutyrate (PDBu; 10 6 M), was significantly reduced in the cells expressing the Ala-943 mutant compared with that observed in cells expressing wild-type enzyme. In contrast, for cells expressing Na + -K + -ATPase 1 in which Ser-943 was mutated to Asp-943, the effect of PDBu was slightly enhanced. The PDBu-induced inhibition was not mediated by activation of the adenosine 3',5'-cyclic monophosphate/PKA system and was not achieved via direct phosphorylation of Ser-943. Sp-5,6-DCl-cBIMPS, a specific PKA activator, increased the phosphorylation of Ser-943, and this was associated with an enhanced response to PDBu. Thus the effect of PKC on rat Na + -K + -ATPase 1 is determined not only by the activity of PKC but also by the state of phosphorylation of Ser-943. adenosine 3',5'-cyclic monophosphate-dependent protein kinase; phorbol ester; COS cells; site-directed mutagenesis; protein kinase C