Citation

Toews JC, Schram V, Weerth SH, Mignery GA, Russell JT. Glia 2007; 55(2): 202-213.

Copyright

(Copyright © 2007, John Wiley and Sons)

DOI

10.1002/glia.20448

PMID

unavailable

Abstract

During action potential conduction, the axonal specializations at the node, together with the adjacent paranodal terminations of the myelin sheath, interact with glial processes that invest the nodal gap. The nature of the mutual signals between axons and myelinating glia, however, are not well understood. Here we have characterized the distribution of inositol 1,4,5-trisphosphate receptors (IP3Rs) in the axoglial apparatus by immunohistochemistry, using known myelin domain-specific markers. While IP3R1 is not expressed in the Schwann cells or the axon, IP3R2 and IP3R3 are expressed in distinct cellular domains, suggesting distinct signaling roles for the two receptors. IP3R3 is the most predominant isoform in Schwann cells, and is expressed in particularly dense patches in the paranodal region. In addition to IP3Rs, two other members of the metabotropic Ca2+ signaling pathway, Gαq, and P2Y1 type of purinoceptors were also found in Schwann cells. Their pattern of expression matches the expression of their signaling partners, the IP3Rs. One interesting finding to emerge from this study is the expression of connexin 32 (Cx32) in close proximity with IP3R3. Although IP3R3 and Cx32 are not colocalized, their expression in the same membrane areas raises the question whether Schwann cell Ca2+ signals either control the function of the gap junctions, or whether the gap junctional channels serve as conduits for rapid radial spread of Ca2+ signals initiated during action potential propagation. Published 2006 Wiley-Liss, Inc.