Altered Intracellular Calcium Homeostasis in Cerebellar Granule Cells of Prion Protein-Deficient Mice.

Abstract: Previous studies have indicated that recombinant cellular prion protein (PrPC), as well as a synthetic peptide of PrPC, affects intracellular calcium homeostasis. To analyze whether calcium homeostasis in neurons is also affected by a loss of PrPC, we performed microfluorometric calcium measurements on cultured cerebellar granule cells derived from prion protein-deficient (Prnp0/0) mice. The resting concentration of intracellular free calcium ([Ca2+]i) was found to be slightly, but significantly, reduced in Prnp0/0 mouse granule cell neurites. Moreover, we observed a highly significant reduction in the [Ca2+]i increase after high potassium depolarization. Pharmacological studies further revealed that the L-type specific blocker nifedipine, which reduces the depolarization-induced [Ca2+]i increase by 66% in wild-type granule cell somas, has no effect on [Ca2+]i in Prnp0/0 mouse granule cells. Patch-clamp measurements, however, did not reveal a reduced calcium influx through voltage-gated calcium channels in Prnp0/0 mice. These data clearly indicate that loss of PrPC alters the intracellular calcium homeostasis of cultured cerebellar granule cells. There is no evidence, though, that this change is due to a direct alteration of voltage-gated calcium channels. [ABSTRACT FROM AUTHOR]