MYELIN BASIC-PROTEIN MESSENGER-RNA LOCALIZATION AND POLYPEPTIDE TARGETING

Myelin basic proteins (MBPs), the major peripheral membrane proteins o f central nervous system (CNS) myelin, are encoded by mRNAs that are s electively segregated to the myelinating processes of oligodendrocytes , In order to test whether the intracellular mechanisms responsible fo r MBP mRNA translocation are oligodendrocyte-specific, or alternativel y, are present in other cell types and may therefore be more general, we have studied the localization of the 14 kD MBP mRNA and its encoded polypeptide (MBP14) in transiently transfected HeLa cells (a cervical carcinoma cell line) and in the rat pheochromocytoma cell line PC12, Unlike the situation in oligodendrocytes in situ, where MBP mRNAs are translocated and become ''centrifugally'' distributed, in both of the non-glial cells MBP mRNA was primarily detected in the perinuclear reg ion, The MBP14 polypeptide was found associated with intracellular mem branes, and not exclusively with the plasma membrane, Our results indi cate that the inability of HeLa and PC12 cells to correctly target MBP mRNAs to the cell periphery leads to a failure to incorporate MBP pol ypeptides directly into the plasma membrane, Further, the data lend cr edence to the concept that MBP mRNA segregation appears to be a specif ic feature of myelin-forming cells which is required for the precise d elivery of the encoded polypeptides to the forming myelin membrane. (C ) 1995 Wiley-Liss, Inc.