Voltage-sensitive calcium channels in osteoblasts: mediators of plasma membrane signalling events

Voltage-Sensitive Calcium Channels (VSCCs) are important cell surface regulators of membrane permeability to Ca2+. In non-excitable cells such as osteoblasts, VSCCs act as cellular transducers of stimulus-secretion coupling, activators of intracellular proteins, and in control of cell growth and differentiation. To obtain information concerning the molecular identity of the osteoblastic VSCC, we used an RT-PCR regional amplification approach. Effort focused on the large membrane-spanning alpha 1 subunit that is responsible for ion translocation. We designed primers using conserved alpha 1 subunit sequences common to many channel isoforms from various tissues and species. The generation of several RT-PCR products from various osteoblastic cell lines and subsequent sequencing of these products indicated that osteoblasts express at least two variants of the L-type VSCC which share regions of identity to the CaCh2 isoform first identified in cardiac myocytes. Our work provides the first molecular evidence for the existence and identity of VSCCs present in osteoblasts.