Biochemistry and Biotechnology
Wiley InterScience Backfile Collection 1832-2000
Chemistry and Pharmacology
The abundance of mitochondrial protein IEF 24 in various Balb C mouse tissues was determined using two-dimensional gel electrophoresis and silver staining. We found that this protein is an abundant component of all mouse tissues so far studied and these included adult brain, heart, intestine, kidney, liver, lung, muscle, skin and tongue. Comparatively little vimenting was observed in most tissues. Indirect immunofluorescent staining of methanol: acetone fixed cryostat sections from various mouse tissues using IEF 24 antibodies confirmed the mitochondrial localization of this protein but did not reveal a preferential distribution of this organelle. In contrast to these results, primary cultures of well-spread fibroblasts from various tissues as well as of kidney epithelial cells showed in all cases the appearance of rows of well-aligned mitochondrial fragments. These results, together with the apparently increased number of vimentin filaments observed in cultured mouse kidney fibroblasts, supported the notion that intermediate-sized filaments of the vimentin type may serve as an anchorage site for the mitochondria in cultured cells. The lack of preferential distribution of the mitochondria observed in kidney fibrolasts in situ, which also exhibited vimentin filaments, may be due to their characteristic morphology. Cultured mouse kidney epithelial cells on the other hand showed only background fluorescence when reacted with the vimentin antibodies but showed abundant intermediate-sized filaments of the keratin type. Based on the above results and considering the fact that many cell types in situ do not synthesize vimentin, it is proposed that both vimentin and keratin type intermediate filaments may serve as an anchorage site for the mitochondria. This proposal does does not necessarily contradict reports which indicate that mitochondria are also bound to microtubules, a possibility also suggested by our studies.
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