The light chain of MAP1A binds to and stabilizes microtubules.

Abstract

Microtubule-associated protein 1A (MAP1A) is expressed in the nervous system during development and its expression parallels an increase in microtubule (MT) stability. Previous studies (Vaillant et al., 1998) revealed that the entire MAP1A protein complex represented by heavy chain and light chain (LC2) and the MAP1A heavy chain alone bind to MTs and have moderate effects on MT stability. To determine if LC2 alone can bind to MTs in vivo, we expressed EGFP-tagged LC2 by transient transfection in HeLa cells. Fluorescence microscopy showed that EGFP-LC2 binds to MTs and alters their distribution. EGFP-LC2 had some effect on intermediate filament distribution, but no effect on actin. EGFP-LC2 also induced formation of stable MTs, as shown by their resistance to the effects of nocodazole and taxol. Co-transfection studies showed that LC2 bound to the N-terminus (AAs 1--281) of MAP1A heavy chain, and that the heavy chain might regulate LC2 activities, by greatly reducing LC2 effects on MTs.