Role of regulator of G protein signaling 2 (RGS2) in Ca(2+) oscillations and adaptation of Ca(2+) signaling to reduce excitability of RGS2-/- cells.
Regulators of G protein signaling (RGS) proteins accelerate the GTPase activity of Galpha subunits to determine the duration of the stimulated state and control G protein-coupled receptor-mediated cell signaling. RGS2 is an RGS protein that shows preference toward Galpha(q). To better understand the role of RGS2 in Ca(2+) signaling and Ca(2+) oscillations, we characterized Ca(2+) signaling in cells derived from RGS2(-/-) mice. Deletion of RGS2 modified the kinetic of inositol 1,4,5-trisphosphate (IP(3)) production without affecting the peak level of IP(3), but rather increased the steady-state level of IP(3) at all agonist concentrations. The increased steady-state level of IP(3) led to an increased frequency of [Ca(2+)](i) oscillations. The cells were adapted to deletion of RGS2 by reducing Ca(2+) signaling excitability. Reduced excitability was achieved by adaptation of all transporters to reduce Ca(2+) influx into the cytosol. Thus, IP(3) receptor 1 was down-regulated and IP(3) receptor 3 was up-regulated in RGS2(-/-) cells to reduce the sensitivity for IP(3) to release Ca(2+) from the endoplasmic reticulum to the cytosol. Sarco/endoplasmic reticulum Ca(2+) ATPase 2b was up-regulated to more rapidly remove Ca(2+) from the cytosol of RGS2(-/-) cells. Agonist-stimulated Ca(2+) influx was reduced, and Ca(2+) efflux by plasma membrane Ca(2+) was up-regulated in RGS2(-/-) cells. The result of these adaptive mechanisms was the reduced excitability of Ca(2+) signaling, as reflected by the markedly reduced response of RGS2(-/-) cells to changes in the endoplasmic reticulum Ca(2+) load and to an increase in extracellular Ca(2+). These findings highlight the central role of RGS proteins in [Ca(2+)](i) oscillations and reveal a prominent plasticity and adaptability of the Ca(2+) signaling apparatus.
Department of Physiology University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75390-9040, USA.
Xinhua
X
Wang
Guojin
G
Huang
Xiang
X
Luo
Josef M
JM
Penninger
Shmuel
S
Muallem
D000222:Adaptation, Physiological; D000818:Animals; D001921:Brain / Q000166:cytology; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels; D020013:Calcium Signaling; D005786:Gene Expression Regulation / Q000502:physiology*; D015544:Inositol 1,4,5-Trisphosphate / Q000096:biosynthesis; D053496:Inositol 1,4,5-Trisphosphate Receptors; D007700:Kinetics; D051379:Mice; D018345:Mice, Knockout; D008861:Microsomes; D010179:Pancreas / Q000166:cytology; D020710:RGS Proteins / Q000235:genetics / Q000502:physiology*; D018160:Receptors, Cytoplasmic and Nuclear; D013363:Submandibular Gland / Q000166:cytology
D015220:Calcium Channels; D053496:Inositol 1,4,5-Trisphosphate Receptors; D020710:RGS Proteins; D018160:Receptors, Cytoplasmic and Nuclear; C105345:Rgs2 protein, mouse; D015544:Inositol 1,4,5-Trisphosphate; D002118:Calcium