Molecular and functional characteristics of MAP-2a: Ability of MAP-2a versus MAP-2b to induce stable microtubules in COS cells

✍ Scribed by Kalcheva, Nellie ;Rockwood, Julia M. ;Kress, Yvonne ;Steiner, Ari ;Shafit-Zagardo, Bridget

• Publisher: John Wiley and Sons
• Year: 1998
• Tongue: English
• Weight: 654 KB
• Volume: 40
• Category: Article
• ISSN: 0886-1544
• DOI: 10.1002/(sici)1097-0169(1998)40:3<272::aid-cm6>3.0.co;2-f

✦ Synopsis

Microtubule-associated protein-2 (MAP-2) is a prominent cytoskeletal protein in the mammalian nervous system. Two high-molecular-weight (HMW) MAP-2 isoforms, MAP-2a and MAP-2b, are developmentally regulated. MAP-2b is expressed through the life of the neuron, while MAP-2a expression coincides with the time of synaptic formation. MAP-2a and MAP-2b differ in size by approximately 10 kD. Attempts to differentiate MAP-2a from MAP-2b led to the identification of additional exons; exons 7A, 8, 13, and 16. The focus of the present study was to define the complete molecular composition of MAP-2a that was prerequisite for investigating the functional characteristic of the MAP-2a protein. Detailed examination of rat brain mRNA by Northern blot analysis and RT-PCR showed that MAP-2a contains only exon 8 in addition to the exons found in the MAP-2b transcript. Exons 7A, 13, and 16 are not present in the MAP-2a transcript. Antibody generated to exon 8 expressed protein, immunoprecipitated a HMW protein from adult rat brain that co-migrated with MAP-2a and was immunopositive with other MAP-2 antibodies. Comparative transfections of full-length MAP-2a and MAP-2b cDNA into COS-7 cells demonstrated that MAP-2a influenced the microtubule network differently than MAP-2b by inducing rapid and stable microtubule bundle formation even in the presence of nocodazole. Cell