Expression of the Plasma Membrane Ca2+-ATPase in Myogenic Cells

Abstract

To study the physiological function of the plasma membrane calmodulin-dependent calcium ATPase (PMCA) in intact cells, L6 myogenic cell lines stably overexpressing the human PMCA isoform 4CI ‫؍(‬ human PMCA isoform 4b) were generated. Several independent L6 clones and controls stably transfected with the empty expression vector were analyzed in detail. The resting cytosolic calcium level in hPMCA4CI-overexpressing muscle cells (measured by the Fura-2 method) was significantly reduced by 20 -30% compared with controls. This was shown in a cytosolic window of 1322 single cells (p < 0.01). Furthermore, the differentiation process of these cells was remarkably accelerated compared with control myoblasts and parental nontransfected L6 cells as assessed by multinucleated myotube formation and creatine phosphokinase activity elevation. After 4 and 6 days of differentiation, PMCA-overexpressing L6 cells from four independent clones displayed a 3-and 4-fold higher creatine phosphokinase activity compared with controls (n ‫؍‬ 5, p < 0.02). These results may extend the concept of the function of the PMCA from simple prevention of calcium overload to an active involvement in intracellular calcium regulation with potentially important consequences for cellular functions.

Isoform-specific up-regulation of plasma membrane Ca2+ATPase expression during colon and gastric cancer cell differentiation

“…To further characterize this homeostatic matrix, in the present work we investigated the expression pattern and the function of plasma membrane Ca 2+ ATPases in various gastric and colon cancer cell lines, and studied the effect of cell differentiation on their expression and activity. Implication of PMCAs in the differentiation of various tissue/cell types has already been published [27][28][29][30][31][32][33]. Our studies, focused on gastric/colon carcinomas, indicate that the major PMCA isoform expressed in these cancer cell lines is PMCA1b, whereas PMCA4b is expressed only at a reduced level.…”

“…Modulations of PMCA expression have been observed during neuronal [27,28] and retinal [29] maturation, in myogenic [30], megakaryoblastoid [31], osteoblast-like [32] and trophoblast-like [33] differentiation models, as well as in cornea [84], in lactating mammary tissue [85] and oral and breast cancer [86,87]. In addition, marked induction of the expression of the SERCA3 endoplasmic reticulum Ca 2+ ATPases has been shown earlier during megakaryocytopoiesis [88], during cell differentiation in various leukemia [21,42] and gastric/ colon cancer cells ( [21,22,89].…”

Calcineurin-independent regulation of plasma membrane Ca2+ ATPase-4 in the vascular smooth muscle cell cycle

“…Indeed, ϳ60% of the c-Myb effect on VSMC proliferation is exerted via PMCA1 repression (22). However, PMCA4 also appeared to be regulated during the cell cycle progression of rat VSMC (23), and overexpression of PMCA4 had been shown to induce terminal differentiation of skeletal myoblasts (19). Given that PMCA4 expression levels in mouse neurons were repressed via calcineurin (18), we sought to examine whether this pathway participated in the cell cycle-regulated [Ca 2ϩ ] i of mouse VSMC.…”

The Plasma Membrane Calcium ATPasesand Their Role as Major New Players in Human Disease

“…Direct evidence that the PMCA may play a role in regulating the differentiation process has been demonstrated upon overexpression of human PMCA4 in rat L6 myoblasts, which led to reduced [Ca 2ϩ ] i , increased myotube formation, and hence accelerated differentiation (148). A spike in intracellular Ca 2ϩ is required for the maturation of a number of precursor cell types (23), while low resting cytosolic Ca 2ϩ is a feature in most mature cells.…”