Study of possible interactions of tubulin, microtubular network, and STOP protein with mitochondria in muscle cells.

Abstract : We studied possible connections of tubulin, microtubular system, and microtubular network stabilizing STOP protein with mitochondria in rat and mouse cardiac and skeletal muscles by confocal microscopy and oxygraphy. Intracellular localization and content of tubulin was found to be muscle type-specific, with high amounts in oxidative muscles, and much lower in glycolytic skeletal muscle. STOP protein localization and content in muscle cells was also muscle type-specific. In isolated heart mitochondria, addition of 1 microM tubulin heterodimer increased apparent K(m) for ADP significantly. Dissociation of microtubular system into free tubulin by colchicine treatment only slightly decreased initially high apparent K(m) for ADP in permeabilized cells, and diffusely distributed free tubulin stayed inside the cells, obviously connected to the intracellular structures. To identify the genes that are specific for oxidative muscle, we developed and applied a method of kindred DNA. The results of sequencing and bioinformatic analysis of isolated cDNA pool common for heart and m. soleus showed that in adult mice the beta-tubulin gene is expressed predominantly in oxidative muscle cells. It is concluded that whereas dimeric tubulin may play a significant role in regulation of mitochondrial outer membrane permeability in the cells in vivo, its organization into microtubular network has a minor significance on that process.