(709.5) Pressure Modulation of Vascular L-type Calcium Channels: implications to the Myogenic Response

Poster Board Number: E29

Galina Mironova (University of Western Ontario), Miguel Baudel (University of California), Victor Flores-Tamez (University of California), Suzanne Brett (University of Western Ontario), Manuel Navedo (University of California), Donald Welsh (University of Western Ontario)

L-type Ca2+ channels govern smooth muscle [Ca2+] and myogenic tone development through mechanisms traditionally tied to voltage control. While essential, questions remain as to whether voltage is the sole regulatory influence or whether L-type Ca2+ channels are additionally mechanosensitive. In this context, this study defined whether and by what mechanisms pressure stimuli modulate L-type Ca2+ channels in rodent (rat amp; mouse) resistance arteries. Experiments extended from single smooth muscle cells (whole-cell/single-channel patch clamp; immunohistochemistry; proximity ligation assay) to intact arteries (pressure myography). Whole-cell patch clamp electrophysiology revealed that pressure stimuli increased the L-type Ca2+ current, a phenomenon that single channel analysis attributed to enhanced functional coupling. Subsequent work noted that pressure-enhanced functional coupling is tied to: 1) PKC-mediated cooperative gating; and 2) subunit trafficking to caveolae. Functional experiments, using 30 mM KCl to elicit a set depolarization (~-40 mV), revealed that tone and cytosolic [Ca2+] responses were more pronounced in arteries pressurized to 80 rather than 20 mmHg. These functional results are in alignment with patch clamp observations and suggest that L-type Ca2+ channels are indeed mechanosensitive. Cumulatively, our results suggest that there is more to L-type Ca2+ channel regulation than voltage and that pressure sensitivity must be carefully weighed in the healthy and diseased setting. Work continues to precisely define the pressure-sensitive signaling complexes within vascular smooth muscle.

Supported by the Canadian Institute for Health Research, National Institute of Health, American Heart Association Postdoctoral Fellowship # 830629 and the Rorabeck Chair in Vascular Biology and Neuroscience.