Longitudinal smooth muscle of the mammalian intestine. A model for Ca2+ signaling by cADPR.
Ca2+ mobilization in muscle cells from the circular muscle layer of the mammalian intestine is mediated by IP3-dependent Ca2+ release. Ca2+ mobilization in muscle from the adjacent longitudinal muscle layer involves a distinct, phosphoinositide-independent pathway. Receptors for contractile agonists in longitudinal muscle cells are coupled via a pertussis toxin-sensitive G protein to activation of PLA2 and formation of arachidonic acid (AA). The latter activates Cl- channels resulting in depolarization of the plasma membrane and opening of voltage-sensitive Ca2+ channels. Ca2+ influx via these channels induces Ca2+ release by activating sarcoplasmic ryanodine receptor/Ca2+ channels. The increase in [Ca2+]i activates membrane-bound ADP ribosyl cyclase, and the resultant formation of cADPR enhances Ca(2+)-induced Ca2+ release.
Kuemmerle
J F
JF
Department of Physiology, Medical College of Virginia, Richmond 23298-0711, USA.
Murthy
K S
KS
Makhlouf
G M
GM
D000246:Adenosine Diphosphate Ribose / Q000031:analogs & derivatives* / Q000502:physiology; D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000502:physiology*; D015220:Calcium Channels / Q000502:physiology; D036563:Cyclic ADP-Ribose; D004789:Enzyme Activation; D006801:Humans; D007422:Intestines / Q000502:physiology*; D009130:Muscle, Smooth / Q000502:physiology*; D010716:Phosphatidylinositols / Q000378:metabolism; D010741:Phospholipases A / Q000378:metabolism; D054467:Phospholipases A2; D015398:Signal Transduction
D015220:Calcium Channels; D010716:Phosphatidylinositols; D036563:Cyclic ADP-Ribose; D000246:Adenosine Diphosphate Ribose; D010741:Phospholipases A; D054467:Phospholipases A2; D002118:Calcium