Caveolae localization and caveolin expressions in Schwann cells of mature rat spinal nerves.

Caveolae are a specific plasmalemmal microdomain which appear as flask-like invaginations and/or vesicles attaching just beneath the plasmalemma. Caveolae are present in many cell types and are found in the Schwann cells that ensheath myelinated and unmyelinated nerve fibers of the peripheral nervous tissues. However, the precise distribution in the Schwann cell plasmalemma and the functional properties of these caveolae remains obscure. The present study revealed: (1) Caveolae are most commonly observed in the Schwann cell plasmalemma of myelinated nerve fibers. (2) Caveolae are principally located in the perikaryal plasmalemma of Schwann cells of the myelinated nerves. (3) Caveolin-1 is expressed strongly in Schwann cell caveolae. (4) Caveolin 2 and 3 are also immunohistochemically detected in Schwann cell caveolae, although the immunoreactivities are slight. The results suggested that caveolae of the peripheral nervous system are involved in cellular activities specific to Schwann cells in myelinated nerve fibers. These caveolae may contain receptors for signaling molecules that could affect the myelinated nerve fibers, and/or proteins related to ion transfer activity. Further studies are necessary in order to clarify the types of proteins associated with Schwann cell caveolae.