Ca2+-sensing transgenic mice: postsynaptic signaling in smooth muscle.
Genetically encoded signaling proteins provide remarkable opportunities to design and target the expression of molecules that can be used to report critical cellular events in vivo, thereby markedly extending the scope and physiological relevance of studies of cell function. Here we report the development of a transgenic mouse expressing such a reporter and its use to examine postsynaptic signaling in smooth muscle. The circularly permutated, Ca2+-sensing molecule G-CaMP (Nakai, J., Ohkura, M., and Imoto, K. (2001) Nat. Biotechnol. 19, 137-141) was expressed in vascular and non-vascular smooth muscle and functioned as a lineage-specific intracellular Ca2+ reporter. Detrusor tissue from these mice was used to identify two separate types of postsynaptic Ca2+ signals, mediated by distinct neurotransmitters. Intrinsic nerve stimulation evoked rapid, whole-cell Ca2+ transients, or "Ca2+ flashes," and slowly propagating Ca2+ waves. We show that Ca2+ flashes occur through P2X receptor stimulation and ryanodine receptor-mediated Ca2+ release, whereas Ca2+ waves arise from muscarinic receptor stimulation and inositol trisphosphate-mediated Ca2+ release. The distinct ionotropic and metabotropic postsynaptic Ca2+ signals are related at the level of Ca2+ release. Importantly, individual myocytes are capable of both postsynaptic responses, and a transition between Ca2+ -induced Ca2+ release and inositol trisphosphate waves occurs at higher synaptic inputs. Ca2+ signaling mice should provide significant advantages in the study of processive biological signaling.
Department of Biomedical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA.
Guangju
G
Ji
Morris E
ME
Feldman
Ke-Yu
KY
Deng
Kai Su
KS
Greene
Jason
J
Wilson
Jane C
JC
Lee
Robyn C
RC
Johnston
Mark
M
Rishniw
Yvonne
Y
Tallini
Jin
J
Zhang
Winthrop G
WG
Wier
Mordecai P
MP
Blaustein
Hong-Bo
HB
Xin
Junichi
J
Nakai
Michael I
MI
Kotlikoff
D000818:Animals; D002118:Calcium / Q000502:physiology*; D020013:Calcium Signaling / Q000235:genetics*; D003001:Cloning, Molecular; D051379:Mice; D008822:Mice, Transgenic; D032342:Muscle Cells / Q000502:physiology; D009130:Muscle, Smooth / Q000502:physiology*; D018995:Myosin Heavy Chains / Q000235:genetics; D011401:Promoter Regions, Genetic; D044169:Receptors, Calcium-Sensing / Q000235:genetics / Q000502:physiology; D011994:Recombinant Proteins / Q000378:metabolism; D015398:Signal Transduction; D013569:Synapses / Q000502:physiology
D044169:Receptors, Calcium-Sensing; D011994:Recombinant Proteins; D018995:Myosin Heavy Chains; D002118:Calcium