Grau E, Felipo V, Miñana M D, Grisolía S
Instituto de Investigaciones Citológicas, Fundación Valenciana de Investigaciones Biomédicas, Spain.
Neurochem Res. 1992 Oct;17(10):967-71. doi: 10.1007/BF00966822.
During experiments studying dietary effects on phosphorylation/dephosphorylation of MAP-2 we found that incubation of microtubules with alkaline phosphatase resulted in extensive proteolysis of MAP-2 but not of tubulin or Tau proteins. In the absence of tubulin, when microtubule-associated proteins (MAPs) were incubated with alkaline phosphatase, MAP-2 was not proteolyzed. This suggests that binding to tubulin induces a conformational change in MAP-2 which makes it more susceptible to proteolysis. The proteolysis of MAP-2 by alkaline phosphatase was prevented by inhibitors of serine proteases, suggesting that the commercial preparation of the enzyme is contaminated by a serine protease and/or that the enzyme also has a weaker proteolytic activity. In addition, selective proteolysis of MAP-2 can be obtained with the metalloprotease collagenase. Brain homogenates are shown to contain a Ca(2+)-dependent protease which selectively degrades MAP-2 bound to tubulin. These results suggest that selective proteolysis of tubulin-bound MAP-2 could play a role in the regulation of microtubule dynamics in response to extracellular signals.
