Cytoskeletal and nuclear localization of myelin oligodendrocytic basic protein isoforms

Abstract

The recently described single copy myelin-associated oligodendrocytic basic protein (Mobp) gene is expressed exclusively in the central nervous system (CNS). The gene encodes a family of small highly basic polypeptides with predicted amino acid lengths of 69, 71, 81, 99 and 170, all of which share a 68 residue amino terminal. Here we report on the subcellular distribution of two of these polypeptides termed MOBP81 and MOBP170 in transiently transfected Cos7 cells using an antibody raised against a region common to all isoforms of MOBP. Additionally, we describe MOBP trafficking in cultured mouse spinal cord oligodendrocytes. Immunostaining for MOBP81 is intense in the perinuclear region and extends throughout the cytoplasm colocalizing with the microtubular cytoskeletal network. Consistent with this we demonstrate that MOBP partitions with the cytoskeletal fraction prepared from myelin. In contrast, although MOBP170 is present in the cytoplasm it does not colocalize with the cytoskeleton and displays a greater variation in distribution. In the majority of transfectants immunostaining is present throughout the karyoplasm but with increased intensity around the nucleolus. Within mouse primary oligodendrocytes endogenous MOBP is present in the cell body and processes colocalizing with the microtubular network. Immunoreactivity is not detectable in the nucleus in these mature oligodendrocytes. These significant differences in MOBP81 and MOBP170 protein kinesis coupled to different expression profiles of their respective message populations may be indicative of both myelin structural and cellular/regulatory functions, respectively, for these polypeptides.

MOBP levels are regulated by Fyn kinase and affect the morphological differentiation of oligodendrocytes

“…In contrast to MBP, which is very abundant in the membrane sheets (Aggarwal et al, 2011), MOBP appeared to be more restricted to the oligodendroglial cytoplasm and larger processes (Fig. 1F), supporting previous observations (Montague et al, 1998).…”

“…As oligodendrocytes tend to extend, spread and retract their processes, MOBP could also stabilize newly formed, lengthened or widened processes while counteracting their retraction. Interestingly, an association of MOBP with microtubules has been observed in cultured oligodendrocytes (Montague et al, 1998), and, here, we show a significant colocalization of α-tubulin with MOBP, of ∼58.3%, in primary oligodendrocytes at 5 DIV when the protein synthesis rate of MOBP appears to be strongly enhanced. It is hence likely that our observed changes in morphological differentiation after the manipulation of MOBP levels are at least in part mediated by the interaction of MOBP with the microtubular network.…”

Subcellular localization of Mayven following expression of wild type and mutant EGFP tagged cDNAs

“…6I). Following guidelines we previously described for Nocodzole treatment of Cos7 transfectants [34] we found that OECs exposed to 30 μM Nocodazole for 3 hrs lead to depolymerisation of the microtubular network as evidenced by the breakdown of the characteristic trebecular staining pattern in the vast majority of the treated cells (Fig. 6J).…”

Oligodendrocytes express functional A1 adenosine receptors that stimulate cellular migration

“…Immunocytochemistry was performed as described (Montague et al, 1998;Yan and Rivkees, 2002). To detect surface antigens, cultures were washed twice with L-15 medium.…”