Charge movement and calcium currents in skeletal muscle fibers are enhanced by GTPγS

✍ Scribed by J. García; R. Gamboa-Aldeco; E. Stefani

• Book ID: 104745134
• Publisher: Springer
• Year: 1990
• Tongue: English
• Weight: 395 KB
• Volume: 417
• Category: Article
• ISSN: 0031-6768
• DOI: 10.1007/bf00370779

✦ Synopsis

G-proteins play several regulatory roles in the cell. They can modulate ionic channels directly or in association with second messengers. In skeletal muscle, G-proteins modulate the activity of calcium channels either by acting directly on the channel and/or through a cAMP-dependent phosphorylating mechanism zg. The activation of G-proteins by GTP-tS can also induce force generation in skinned fibers r. In this paper we studied the effect of GTP,~S on charge movement and calcium currents (Iea) in rat and frog skeletal muscle, using the Vaseline gap technique. We observed an increase in both charge movement and Ie~ after the intracellular addition of 10-100 ~M GTPTS. GDP#S did not have any effect. Addition of protein kinase A catalytic subunit increased the Ie,, probably through a phosphorylation process, but did not modify the charge movement. This suggests that protein kinase A and GTP~tS are acting on different sites of the channel. It can be speculated that G-proteins may have a regulatory role in the excitationcontraction coupling mechanism by a direct effect on charge movement.