C6 cells express a sodium-calcium exchanger/GM1 complex in the nuclear envelope but have no exchanger in the plasma membrane: Comparison to astrocytes
✍ Scribed by Xin Xie; Gusheng Wu; Robert W. Ledeen
- Book ID
- 102906766
- Publisher
- John Wiley and Sons
- Year
- 2004
- Tongue
- English
- Weight
- 904 KB
- Volume
- 76
- Category
- Article
- ISSN
- 0360-4012
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✦ Synopsis
Abstract
Previous work demonstrated the presence of an isoform of Na^+^/Ca^2+^ exchanger in the nuclear envelope of neurons and NG108‐15 cells that is tightly associated with GM1 ganglioside and potentiated by the latter. This contrasted with the Na^+^/Ca^2+^ exchanger(s) in the plasma membrane, which were suggested to associate more loosely with GM1. To study these aspects of Na^+^/Ca^2+^ exchanger expression in nonneuronal neural cells, we have examined nuclear and plasma membrane exchanger patterns in astrocytes and C6 cells, a glia‐derived line. We find both cell types contain the tightly associated exchanger/GM1 complex in the nuclear envelope but, surprisingly, only astrocytes possess Na^+^/Ca^2+^ exchanger activity in the plasma membrane. This is the first reported example of a cell (C6) with Na^+^/Ca^2+^ exchangers in the nuclear envelope but not in the plasma membrane. RT‐PCR established the presence of the NCX1 subtype in C6 cells and both NCX1 and NCX2 in astrocytes. Comparison was made with NG108‐15 cells, which have Na^+^/Ca^2+^ exchangers in both nuclear and plasma membranes, and Jurkat cells, which have no Na^+^/Ca^2+^ exchanger in either membrane. Culturing of C6 cells in the presence dibutyryl‐cAMP caused upregulation of a high molecular weight isoform of the exchanger together with GM1 in the nuclear envelope, resulting in significant elevation of Na^+^/Ca^2+^ exchanger activity in the latter. Application of exogenous GM1 to nuclei from non‐treated cells also potentiated exchanger activity, although to a lesser degree. The Na^+^/Ca^2+^ exchanger/GM1 complex occurs in the inner membrane of the nuclear envelope, suggesting a functional role in transferring Ca^2+^ between nucleoplasm and the envelope lumen. © 2004 Wiley‐Liss, Inc.