Calcium sparklets regulate local and global calcium in murine arterial smooth muscle.
In arterial smooth muscle, protein kinase Calpha (PKCalpha) coerces discrete clusters of L-type Ca2+ channels to operate in a high open probability mode, resulting in subcellular domains of nearly continual Ca2+ influx called 'persistent Ca2+ sparklets'. Our previous work suggested that steady-state Ca2+ entry into arterial myocytes, and thus global [Ca2+]i, is regulated by Ca2+ influx through clusters of L-type Ca2+ channels operating in this persistently active mode in addition to openings of solitary channels functioning in a low-activity mode. Here, we provide the first direct evidence supporting this 'Ca2+ sparklet' model of Ca2+ influx at a physiological membrane potential and external Ca2+ concentration. In support of this model, we found that persistent Ca2+ sparklets produced local and global elevations in [Ca2+]i. Membrane depolarization increased Ca2+ influx via low-activity and high-activity persistent Ca2+ sparklets. Our data indicate that Ca2+ entering arterial smooth muscle through persistent Ca2+ sparklets accounts for approximately 50% of the total dihydropyridine-sensitive (i.e. L-type Ca2+ channel) Ca2+ influx at a physiologically relevant membrane potential (-40 mV) and external Ca2+ concentration (2 mm). Consistent with this, inhibition of basal PKCalpha-dependent persistent Ca2+ sparklets decreased [Ca2+]i by about 50% in isolated arterial myocytes and intact pressurized arteries. Taken together, these data support the conclusion that in arterial smooth muscle steady-state Ca2+ entry and global [Ca2+]i are regulated by low-activity and PKCalpha-dependent high-activity persistent Ca(2+) sparklets.
Amberg
Gregory C
GC
Department of Physiology and Biophysics, University of Washington Box 357290, Seattle, WA 98195, USA.
Navedo
Manuel F
MF
Nieves-Cintrón
Madeline
M
Molkentin
Jeffery D
JD
Santana
Luis F
LF
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020746:Calcium Channels, L-Type / Q000502:physiology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015640:Ion Channel Gating / Q000502:physiology*; D008564:Membrane Potentials / Q000502:physiology; D008638:Mesenteric Arteries / Q000166:cytology / Q000502:physiology; D051379:Mice; D018345:Mice, Knockout; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000502:physiology*; D032389:Myocytes, Smooth Muscle / Q000201:enzymology; D018408:Patch-Clamp Techniques; D051571:Protein Kinase C-alpha / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases / Q000037:antagonists & inhibitors / Q000378:metabolism; D019284:Thapsigargin / Q000494:pharmacology; D014655:Vascular Resistance / Q000502:physiology
D020746:Calcium Channels, L-Type; D004791:Enzyme Inhibitors; D019284:Thapsigargin; D051571:Protein Kinase C-alpha; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D002118:Calcium