Protein kinases A and C phosphorylate purified Ca2+-ATPase from rat cortex, cerebellum and hippocampus1A preliminary report of the PKA- and PKC-mediated phosphorylation of Ca2+-ATPase purified from rat brain was presented at the FEBS Special Meeting: Cell Signalling Mechanisms, Amsterdam, The Netherlands, June 29–July 3, 1997.1

Abstract

The plasma membrane Ca2+-ATPase (PMCA), the enzyme responsible for the maintenance of intracellular calcium homeostasis, is regulated by several independent mechanisms. In this paper we report that the protein kinases A and C differentially activate the Ca2+-ATPase purified from synaptosomal membranes of rat cortex, cerebellum and hippocampus. The effect of protein kinases was more pronounced for the cortical enzyme, whereas cerebellar and hippocampal Ca2+-ATPases were activated to a lesser degree. The preparation of Ca2+-ATPase contained the phosphoamino acids, i.e., P-Ser and P-Thr, indicating that the enzyme was purified in phosphorylated state. The phosphorylation of Ca2+-ATPase by PKA and PKC increased the amount of phosphoamino acids, but in a region-dependent manner. Using the specific antibodies against N-terminal portion of four main PMCA isoforms we have characterized the isoforms composition of Ca2+-ATPase purified from the nervous endings of examined brain areas. Our results indicate that the activity of calcium pump is related to its phosphorylated state, and that the phosphorylation is region-dependent. Moreover, the differences observed could be related to the composition of PMCA isoforms in the different brain areas. Phosphorylation of the plasma membrane Ca2+-ATPase appears to be a mechanism to control its activity. The results support also the possible involvement of PKA and PKC.

Ca2+-dependent Protein Kinase-A Modulation of the Plasma Membrane Ca2+-ATPase in Parotid Acinar Cells

“…Physiologically one might expect PMCA activity to be potentiated only when [ (5). However, the lack of any measurable PMCA phosphorylation by forskolin alone is at variance with previous studies (31,48,(52)(53)(54). Such differences could be explained partly by the in vitro phosphorylation assays utilized by some of the above studies in which purified PMCA was used.…”

Long-term modulation of mitochondrial Ca2+ signals by protein kinase C isozymes

“…Second, the Ca 2+ response itself can be modified by a previous activation of PKC. This notion is supported by the presence of consensus sequences for PKC phosphorylation in important proteins related with Ca 2+ homeostasis such as the IP3 receptor ( Willems et al, 1989 ; Nucifora et al, 1995 ), the Ca 2+ ATPase of the plasma membrane ( Zylinska et al, 1998 ), and several agonist receptors ( Francesconi and Duvoisin, 2000 ). This modulatory effect was recently demonstrated by Montero et al (2003) , who showed that PKC inhibition (through the use of a wide-spectrum blocker that guaranteed the inhibition of all isozymes) drastically reduced the agonist-dependent Ca 2+ responses in HeLa cells.…”

RACK1, A multifaceted scaffolding protein: Structure and function

“…Another possibility to explain the multiple functions of RACK1 is that although the protein itself is ubiquitously expressed, its binding partners are not. For example, RACK1 is ubiquitously expressed in the adult mouse brain, however, a much more restricted expression pattern is observed for PKCβII [71,228]. Interestingly, as described above, RACK1 can be associated with different binding partners in different brain regions.…”