Role of protein kinase C in 1,25(OH)2-vitamin D3 modulation of intracellular calcium during development of skeletal muscle cells in culture

Abstract

Regulation of muscle cell Ca(2+) metabolism by 1, 25-dihydroxy-vitamin D(3) [1,25(OH)(2)D(3)] is mediated by the classic nuclear mechanism and a fast, nongenomic mode of action that activates signal transduction pathways. The role of individual protein kinase C (PKC) isoforms in the regulation of intracellular Ca(2+) levels ([Ca(2+)](i)) by the hormone was investigated in cultured proliferating (myoblasts) and differentiated (myotubes) chick skeletal muscle cells. 1,25(OH)(2)D(3) (10(-9) M) induced a rapid (30- to 60-s) and sustained (>5-min) increase in [Ca(2+)](i) which was markedly higher in myotubes than in myoblasts. The effect was suppressed by the PKC inhibitor calphostin C. In differentiated cells, PKC activity increased in the particulate fraction and decreased in cytosol to a greater extent than in proliferating cells after 5-min treatment with 1,25(OH)(2)D(3). By Western blot analysis, these changes were correlated to translocation of the PKC alpha isoform from cytosol to the particulate fraction, which was more pronounced in myotubes than in myoblasts. Specific inhibition of PKC alpha activity using antibodies against this isoform decreased the 1, 25(OH)(2)D(3)-induced [Ca(2+)](i) sustained response associated with Ca(2+) influx through voltage-dependent calcium channels. Neomycin, a phospholipase C (PLC) inhibitor, blocked its effects on [Ca(2+)](i), PKC activity, and translocation of PKC alpha. Exposure of myotubes to 1,2-dioleyl-rac-glycerol (1,2-diolein), also increased [Ca(2+)](i), PKC activity, and the amount of PKC alpha associated with the particulate fraction. Changes in [Ca(2+)](i) induced by diolein were inhibited by calphostin C and nifedipine. The results indicate that PKC alpha activation via PLC-catalyzed phosphoinositide hydrolysis is part of the mechanism by which 1, 25(OH)(2)D(3) regulates muscle intracellular Ca(2+) through modulation of the Ca(2+) influx pathway of the Ca(2+) response to the sterol.

Sphingosine 1-phosphate induces Ca2+ transients and cytoskeletal rearrangement in C2C12 myoblastic cells

“…Moreover, the presence of these receptors at the cell surface, where no voltagegated Ca 2ϩ currents were ever seen, further indicates the existence of "immature" L-type channels in undifferentiated C 2 C 12 myoblasts. Nevertheless, a possible effect of SPP on these channels during muscle cell differentiation should be taken into account in view of the findings that L-type Ca 2ϩ channels of cardiac muscle cells (21) and developing skeletal muscle cells (10,46) are modulated by PKC activation, which is a critical step in the signal transduction of exogenous SPP in C 2 C 12 cells (30). Moreover, activation of L-type Ca 2ϩ channels, which involves phosphorylation of both ␣-and ␤-subunits, may occur whether or not the auxiliary subunits are coexpressed (42).…”

Membrane Initiated Effects of 1α,25-Dihydroxyvitamin D3 in Prostate Cancer Cells: Effects on AP1 and CREB Mediated Transcription

“…Alternatively, the receptor could form different complexes that upon activation start unique signal cascades. An example of a similar observation is membrane initiated signaling in skeletal muscle, where six different signaling pathways have been described for 1α,25(OH) 2 D 3 (Vasquez et al, 1996;Capiati et al, 2000;Dirks-Naylor and Lennon-Edwards, 2011). The point that there are two different vitamin D receptors (VDR, PDIA3) associated with the cell membrane (Holmen et al, 2009;Karlsson et al, 2010) and that PDIA3 has been suggested to form a trimer with at least three high affinity binding sites (Karlsson et al, 2010) make us to postulate that depending on the docking site of 1α,25(OH) 2 D 3 to the receptor, the resulting change in three dimensional structure of the hormone-receptor complex, starts a subsequent signaling cascade.…”

Effets du décocté de Biophytum petersianum (Oxalidaceae) sur la libération du calcium du réticulum sarcoplasmique des cellules musculaires squelettiques

“…L'objectif de ce travail est d'explorer les effets de l'extrait sur l'homéos-tasie du calcium intracellulaire, puisqu'il a été montré que l'augmentation de ce cation divalent pouvait induire l'hypertension artérielle des patients [17]. Nous avons choisi de travailler avec les cellules musculaires squelettiques de rats nouveau-nés pour des raisons suivantes : -les cellules musculaires squelettiques, en culture primaire, présentent avec les cellules musculaires lisse et cardiaque les mêmes mécanismes de régulation du calcium libre intracellulaire [4,5], ces mécanismes étant absents au niveau du muscle squelettique adulte ; -les différents mécanismes impliqués dans le contrôle de l'homéostasie du calcium libre intracellulaire sont bien connus au niveau de la cellule musculaire squelettique ;…”