Expression of Rab GTP-binding proteins during oligodendrocyte differentiation in culture

Oligodendrocytes (OLs) synthesize and transport vast amounts of proteins an d lipids from the cell body to the morphologically and biochemically distin ct domains of the myelin membrane. From our prediction that regulators of v esicular transport should be up-regulated at the time of myelin production, we hypothesized that the upregulated and unidentified small GTPases found by Huber et al. [1994a] may be Rab proteins. We have analyzed the mRNA expr ession of rabs in OLs, and have detected rabs 10, 11b, 18, 24, 26, and 28 i n addition to rabs that were found previously. Our data show that among the Rabs so far far detected during differentiation, only Rabs 5a and 8a exhib ited up-regulation in addition to the previously published Rab3a (Madison e t al. [1999], J. Neurochem. 72: 988-998). We discuss the limited extent of up-regulation of rabs in the context of the presumed necessity for an incre ase in Rab activity during myelin assembly. (C) 2000 Wiley-Liss, Inc.