Calcium oscillation linked to pacemaking of interstitial cells of Cajal: requirement of calcium influx and localization of TRP4 in caveolae.
Interstitial cells of Cajal (ICC) are considered to be pacemaker cells in gastrointestinal tracts. ICC generate electrical rhythmicity (dihydropyridine-insensitive) as slow waves and drive spontaneous contraction of smooth muscles. Although cytosolic Ca(2+) has been assumed to play a key role in pacemaking, Ca(2+) movements in ICC have not yet been examined in detail. In the present study, using cultured cell clusters isolated from mouse small intestine, we demonstrated Ca(2+) oscillations in ICC. Fluo-4 was loaded to the cell cluster, the relative amount of cytosolic Ca(2+) was recorded, and ICC were identified by c-Kit immunoreactivity. We specifically detected Ca(2+) oscillation in ICC in the presence of dihydropyridine, which abolishes Ca(2+) oscillation in smooth muscles. The oscillation was coupled to the electrical activity corresponding to slow waves, and it depended on Ca(2+) influx through a non-selective cation channel, which was SK&F 96365-sensitive and store-operated. We further demonstrated the presence of transient receptor potential-like channel 4 (TRP4) in caveolae of ICC. Taken together, the results infer that the Ca(2+) oscillation in ICC is intimately linked to the pacemaker function and depends on Ca(2+) influx mediated by TRP4.
Torihashi
Shigeko
S
Department of Anatomy, Nagoya University Graduate School of Medicine, Nagoya 466-8550, Japan. storiha@med.nagoya-u.ac.jp
Fujimoto
Toyoshi
T
Trost
Claudia
C
Nakayama
Shinsuke
S
D000818:Animals; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000187:drug effects / Q000378:metabolism*; D027682:Cation Transport Proteins; D021941:Caveolae / Q000378:metabolism*; D017615:Enteric Nervous System / Q000166:cytology / Q000378:metabolism* / Q000502:physiology; D007093:Imidazoles / Q000494:pharmacology; D007150:Immunohistochemistry; D017136:Ion Transport; D051379:Mice; D008807:Mice, Inbred BALB C; D016253:Microscopy, Immunoelectron; D019009:Proto-Oncogene Proteins c-kit / Q000378:metabolism; D050052:TRPC Cation Channels
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D027682:Cation Transport Proteins; D007093:Imidazoles; D050052:TRPC Cation Channels; C489571:TRPC4 ion channel; D019009:Proto-Oncogene Proteins c-kit; C063159:1-(2-(3-(4-methoxyphenyl)propoxy)-4-methoxyphenylethyl)-1H-imidazole; D002118:Calcium