Role of perinuclear mitochondria in the spatiotemporal dynamics of spontaneous Ca2+ waves in interstitial cells of Cajal-like cells of the rabbit urethra.
OBJECTIVE
Although spontaneous Ca(2+) waves in interstitial cells of Cajal (ICC)-like cells (ICC-LCs) primarily arise from endoplasmic reticulum (ER) Ca(2+) release, the interactions among mitochondrial Ca(2+) buffering, cellular energetics and ER Ca(2+) release in determining the spatiotemporal dynamics of intracellular Ca(2+) remain to be elucidated.


METHODS
Spontaneous Ca(2+) transients in freshly isolated ICC-LCs of the rabbit urethra were visualized using fluo-4 Ca(2+) imaging, while the intracellular distribution of mitochondria was viewed with MitoTracker Red.


RESULTS
Spontaneous Ca(2+) waves invariably originated from the perinuclear region where clusters of mitochondria surround the nucleus. Perinuclear Ca(2+) dynamics were characterized by a gradual rise in basal Ca(2+) that preceded each regenerative Ca(2+) transient. Caffeine evoked oscillatory Ca(2+) waves originating from anywhere within ICC-LCs. Ryanodine or cyclopiazonic acid prevented Ca(2+) wave generation with a rise in basal Ca(2+), and subsequent caffeine evoked a single rudimentary Ca(2+) transient. Inhibition of glycolysis with 2-deoxy-glucose or carbonyl cyanide 3-chlorophenylhydrazone, a mitochondrial protonophore, increased basal Ca(2+) and abolished Ca(2+) waves. However, caffeine still induced oscillatory Ca(2+) transients. Mitochondrial Ca(2+) uptake inhibition with RU360 attenuated Ca(2+) wave amplitudes, while mitochondrial Ca(2+) efflux inhibition with CGP37157 suppressed the initial Ca(2+) rise to reduce Ca(2+) wave frequency.


CONCLUSIONS
Perinuclear mitochondria in ICC-LCs play a dominant role in the spatial regulation of Ca(2+) wave generation and may regulate ER Ca(2+) release frequency by buffering Ca(2+) within microdomains between both organelles. Glycolysis inhibition reduced mitochondrial Ca(2+) buffering without critically disrupting ER function. Perinuclear mitochondria may function as sensors of intracellular metabolites.
Hashitani
Hikaru
H
Department of Cell Physiology, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan. hasitani@med.nagoya-cu.ac.jp
Hashiatni
Hikaru
H
Lang
Richard J
RJ
Suzuki
Hikaru
H
D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism / Q000502:physiology; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D002998:Clonazepam / Q000031:analogs & derivatives / Q000494:pharmacology; D003847:Deoxyglucose / Q000494:pharmacology; D004721:Endoplasmic Reticulum / Q000378:metabolism; D006019:Glycolysis / Q000187:drug effects / Q000502:physiology; D006835:Hydrazones / Q000494:pharmacology; D007211:Indoles / Q000494:pharmacology; D056885:Interstitial Cells of Cajal / Q000378:metabolism / Q000502:physiology*; D008297:Male; D008928:Mitochondria / Q000502:physiology*; D011817:Rabbits; D017975:Ruthenium Compounds / Q000494:pharmacology; D012433:Ryanodine / Q000494:pharmacology; D013841:Thiazepines / Q000494:pharmacology; D014521:Urethra / Q000166:cytology / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*
D006835:Hydrazones; D007211:Indoles; C112020:Ru 360; D017975:Ruthenium Compounds; D013841:Thiazepines; C070053:carbonyl 3-chlorophenylhydrazone; D012433:Ryanodine; D002110:Caffeine; D002998:Clonazepam; C079032:CGP 37157; D003847:Deoxyglucose; D002118:Calcium; C000543:cyclopiazonic acid