Key result
Cerebellar granule cells expressed NCKX2, NCKX3, NCKX4, and NCX3 with K-dependent Ca2+ accumulation, whereas astrocytes primarily expressed NCX1.
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Numerous isoforms of plasmalemmal K-dependent (NCKX) and K-independent (NCX) Na+/Ca2+ exchangers are expressed in the brain. The physiological functions of each isoform are presently unknown. Therefore, in this study, we compared expression of NCKX and NCX transcripts between primary cultures of cerebellar granule cells, and astrocytes. Northern blot analysis showed that granule cells expressed NCKX2, NCKX3, NCKX4 and NCX3, whereas astrocytes expressed primarily NCX1. Consistent with this molecular characterization, a significant fraction of 45Ca2+ accumulation in Na-loaded granule cells, but not in astrocytes, depended on external K+. This is the first demonstration of native NCKX activity in neurons derived from the central nervous system. Our data suggest that NCKX isoform expression may correspond to the unique Ca2+ homeostasis requirements of neurons.
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Kiedrowski et al. (2002) studied this question. Cerebellar granule cells vs. Astrocytes was evaluated on Expression of NCKX and NCX transcripts and K-dependent 45Ca2+ accumulation. Cerebellar granule cells expressed NCKX2, NCKX3, NCKX4, and NCX3 with K-dependent Ca2+ accumulation, whereas astrocytes primarily expressed NCX1.
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