The in vitro degradation of microtubule-associated protein 2 (MAP-2) and spectrin by the calcium-dependent neutral protease calpain was studied. Five major results are reported. First, MAP-2 isolated from twice-cycled microtubules (2XMT MAP-2) was extremely sensitive to calpain-induced hydrolysis. Even at an enzyme-to-substrate ratio (wt/ wt) of 1:200, 2XMT MAP-2 was significantly degraded by calpain. Second, MAP-2 purified from the total brain heat-stable fraction (total MAP-2) was significantly more resistant to calpain-induced hydrolysis compared with 2XMT MAP-2. Third, MAP-2a and MAP-2b were proteolyzed similarly by calpain, although some relative resistance of MAP-2b was observed. Fourth, the presence of calmodulin significantly increased the extent of calpain-induced hydrolysis of the α-subunit of spectrin. Fifth, the two neuronal isoforms of brain spectrin (240/235 and 240/235E, referred to as α/βN and α/ βE, respectively) showed different sensitivities to calpain. αN-spectrin was significantly more sensitive to calpain-induced degradation compared to αE-spectrin. Among other things, these results suggest a role for the calpain-induced degradation of MAP-2, as well as spectrin, in such physiological processes as alterations in synaptic efficacy, dendritic remodeling, and in pathological processes associated with neurodegeneration.
|Original language||English (US)|
|Number of pages||9|
|Journal||Journal of neurochemistry|
|State||Published - May 1991|
- Microtubule-associated protein 2
ASJC Scopus subject areas
- Cellular and Molecular Neuroscience