Microtubule associated protein (MAP1B) is present in cultured oligodendrocytes and co‐localizes with tubulin

Abstract

Differentiation of oligodendrocytes is accompanied by the extension of processes and the assembly of the myelin membrane. It is likely that the cytoskeleton plays an important role in this process in terms of changes in cell shape, transport of myelin components, and organization of the myelin membrane. Oligodendrocytes contain microtubules (MT) which associate with other components of the cytoskeleton, and microtubule associated proteins (MAPs) may mediate some of these interactions. In this study we have shown the presence of MAP1B in oligodendrocytes grown in primary glial cultures by double-label immunofluorescence using antibodies to galactocerebroside (GC) and MAP1B. The staining of the cultures showed that GC-positive oligodendrocytes were also stained with MAP1B antibodies. However, MAP1B stain was limited to cell bodies and processes, whereas GC stain was also seen in flattened membrane sheets and punctate staining in processes. MAP1B staining was also compared with that of myelin proteolipid (PLP), myelin basic protein (MBP) and beta-tubulin in secondary glial cultures that were enriched for oligodendrocytes. The results showed a typical staining of cell bodies and membranous profiles using PLP antibodies, and the staining of cell bodies and flattened regions of membranous sheets by MBP antibodies. In contrast, both polyclonal and monoclonal antibodies to MAP1B showed a uniform diffuse staining of cell bodies, major processes, and fine interconnected processes. Double-labeling of the cells showed that MAP1B was co-localized with tubulin, but was not present in glial fibrillary acidic protein (GFAP)-positive astrocytes. Western and Northern blot analyses of primary glial cultures showed that MAP1B had a molecular mass of 320 kDa and a mRNA of 10 kb. These values are identical to those previously reported for brain MAP1B (Safaei and Fischer, 1989) and demonstrate the presence of MAP1B in oligodendrocytes.

Class III β-Tubulin isotype (β III) in the adrenal medulla: III. Differential expression of neuronal and glial antigens identifies two distinct populations of neuronal and glial-like (sustentacular) cells in the PC12 rat pheochromocytoma cell line maintained in a gelfoam matrix system

“…Also, a later decrease in the levels of (phosphorylationindependent) MAP1B has been shown in cultures of hippocampal neurons (Boyne et al, 1995). It is noteworthy that MAP1B is also present in oligodendrocytes (Fischer et al, 1990).…”

Human myelin proteome and comparative analysis with mouse myelin

“…First, we compared our database with other studies, primarily the transcriptome database of OLs, neurons, and astrocytes that were isolated from rodent brains (8,(12)(13)(14)(15)(16)(17)(18). Among the 308 proteins, there were at least 111 proteins in our myelin proteome whose mRNA or protein was expressed by OLs (Fig.…”

“…Many of these transcripts are expressed at higher levels in OL-rich white over gray matter, shown as fold enrichment (i.e., W/G ratio). In addition, to help ascertain the cellular origins of the proteins identified in our proteome, the relative enrichment of their transcripts in purified OLs (red squares in column O), neurons (column N), or astrocytes (column A) was determined through analysis of the transcriptome database of Cahoy et al (8) and other studies (12)(13)(14)(15)(16)(17)(18) of OLs (tan squares in column O). Comparison of the identified proteins in this study with other myelin proteomes (4 -7) has confirmed more than 50% of the identified proteins and revealed the presence of 163 additional proteins in myelin that have not previously been reported in any other proteome (column U).…”

“…In addition to septin-4 and septin-7, which were verified by immunoblot analysis, several other members of the septin family (septins 2, 5, 6, 8, 9, and 11) were also detected in the myelin proteome. Microtubule proteins that were identified included ␤4-tubulin, selectively expressed by OLs (16); microtubuleassociated protein (MAP) 1B, expressed by OLs in vitro (12); and MAP1A, MAP2, and Tau. Interestingly, Band 4.1G and tubulin polymerization-promoting protein, reported in OLs (26), have been identified and verified by immunoblot to be present in myelin.…”

QKI Binds MAP1B mRNA and Enhances MAP1B Expression during Oligodendrocyte Development

“…MAP1B expression is markedly upregulated during neurite outgrowth in various types of neurons (Gordon-Weeks and Fischer, 2000), and MAP1B knockout mice exhibit a range of abnormalities in axonal extension and path finding (Meixner et al, 2000;Gonzalez-Billault et al, 2001;Bouquet et al, 2004). More recent studies indicated that MAP1B expression is not restricted in neurons, but also is detected in oligodendrocytes and Schwann cells that produce myelin in the central and peripheral nervous system (CNS and PNS), respectively (Fischer et al, 1990;Ma et al, 1999). In particular, MAP1B expression is elevated in oligodendrocytes that initiate ensheathment of neuronal axons during normal brain development (Wu et al, 2001) as well as in Schwann cells during nerve regeneration (Ma et al, 1999).…”