Molecular and functional characteristics of MAP-2a: ability of MAP-2a versus MAP-2b to induce stable microtubules in COS cells.
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.
Department of Pathology, Albert Einstein College of Medicine, Bronx, New York 10461, USA.
N
N
Kalcheva
J M
JM
Rockwood
Y
Y
Kress
A
A
Steiner
B
B
Shafit-Zagardo
D000818:Animals; D015152:Blotting, Northern; D019556:COS Cells; D008869:Microtubule-Associated Proteins / Q000502:physiology*; D008870:Microtubules / Q000737:chemistry*; D008970:Molecular Weight; D015739:Nocodazole / Q000494:pharmacology; D016133:Polymerase Chain Reaction / Q000379:methods; D051381:Rats; D014158:Transcription, Genetic; D014162:Transfection
D008869:Microtubule-Associated Proteins; D015739:Nocodazole