Involvement of the Ca2+/calmodulin-dependent protein kinase II pathway in the Ca2+-mediated regulation of the capacitative Ca2+ entry in Xenopus oocytes.
Activation of the phosphoinositide transduction pathway induces capacitative Ca2+ entry in Xenopus oocytes. This can also be evoked by intracellular injection of Ins(1,4.5)P3, external application of thapsigargin and/or incubation in a Ca2+-free medium. Readmission of Ca2+ to voltage-clamped, thapsigargin-treated Xenopus oocytes triggers Ca2+-dependent Cl- current variations that reflect capacitative Ca2+ entry. Inhibition of Ca2+/calmodulin-dependent protein kinase II (CaMKII) by specific peptides markedly increased the amplitude of the transients, suggesting an involvement of the CaMKII pathway in the regulation of capacitative Ca2+ entry. Biochemical studies provide evidence for the activation of CaMKII in response to the development of capacitative Ca2+ entry. In effect, a CaMKII assay in vivo allows us to postulate that readmission of Ca2+ to thapsigargin-treated oocytes can induce a burst of CaMKII activity. Finally, analysis of the Cl- transient kinetics at high resolution of time suggests that CaMKII inhibition blocks the onset of the inactivation process without affecting the activation rate. We therefore postulate that CaMKII might participate in a negative feedback regulation of store-depletion-evoked Ca2+ entry in Xenopus oocytes.
Matifat
F
F
Laboratoire de Neurobiologie Cellulaire, Université de Picardie Jules Verne, Faculté des Sciences, Amiens, France.
Fournier
F
F
Lorca
T
T
Capony
J P
JP
Brûlé
G
G
Collin
T
T
D000595:Amino Acid Sequence; D000818:Animals; D002118:Calcium / Q000378:metabolism* / Q000502:physiology*; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000502:physiology*; D018118:Chloride Channels / Q000187:drug effects / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004594:Electrophysiology; D004789:Enzyme Activation; D005110:Extracellular Space / Q000378:metabolism; D008969:Molecular Sequence Data; D009865:Oocytes / Q000187:drug effects / Q000378:metabolism*; D010455:Peptides / Q000494:pharmacology; D014982:Xenopus laevis
D018118:Chloride Channels; D010455:Peptides; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D002118:Calcium