Expression of voltage‐gated Ca 2+ channel subtypes in cultured astrocytes

• Published in: Glia 2003-03, Vol.41 (4), p.347-353
• Main Authors: Latour, Isabelle, Hamid, Jawed, Beedle, Aaron M., Zamponi, Gerald W., Macvicar, Brian A.
• Format: Article
• Language: English
• ISSN: 0894-1491; 1098-1136
• DOI: 10.1002/glia.10162

Transient intracellular [Ca 2+ ] increases in astrocytes from influx and/or release from internal stores can release glutamate and thereby modulate synaptic transmission in adjacent neurons. Electrophysiological studies have shown that cultured astrocytes express voltage‐dependent Ca 2+ channels but their molecular identities have remained unexplored. We therefore performed RT‐PCR analysis with primers directed to different voltage‐gated Ca 2+ channel α 1 subunits. In primary cultures of astrocytes, we detected mRNA transcripts for the α 1B (N‐type), α 1C (L‐type), α 1D (L‐type), α 1E (R‐type), and α 1G (T‐type), but not α 1A (P/Q‐type), voltage‐gated Ca 2+ channels. We then used antibodies against all of the Ca 2+ channel subunits to confirm protein expression, via Western blots, and localization by means of immunocytochemistry. In Western blot analysis, we observed immunoreactive bands corresponding to the appropriate α 1 subunit proteins. Western blots showed an expression pattern similar to PCR results in that we detected proteins for the α 1B (N‐type), α 1C (L‐type), α 1D (L‐type), α 1E (R‐type), and α 1G (T‐type), but not α 1A (P/Q‐type). Using immunocytochemistry, we observed Ca 2+ channel expression for these subunits in punctate clusters on plasmamembrane of GFAP‐expressing astrocytes. These results confirm that cultured astrocytes express corresponding proteins to several high‐ and low‐threshold Ca 2+ channels but not α 1A (P/Q‐type). Overall, our data indicate that astrocytes express multiple types of voltage‐gated Ca 2+ channels, hinting at a complex regulation of Ca 2+ homeostasis in glial cells. GLIA 41:347–353, 2003. © 2003 Wiley‐Liss, Inc.