期刊
JOURNAL OF BIOLOGICAL CHEMISTRY
卷 278, 期 32, 页码 30005-30014出版社
AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
DOI: 10.1074/jbc.M300614200
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The present study was designed to determine the specific roles played by lysosomes and proteasomes in the degradation of Cx43 in both gap junctional intercellular communication-deficient MDA-MB-231 and -competent BICR-M1R(k) cells. In MDA-MB-231 cells, immunolocalization and brefeldin A protein transport blocking studies revealed that there was a propensity for newly synthesized Cx43 to be transported to lysosomes. On the other hand, light and electron microscopic analysis of BICR-M1R(k) cells showed that Cx43 gap junctions were prevalent with a subpopulation of intracellular Cx43 localized to lysosomes. In both cell types, Western blots revealed a notable increase in total cellular Cx43 in response to lysosome inhibitors. Interestingly, lactacystin inhibition of proteosomal degradation in MDA-MB-231 cells resulted in a marked increase in phosphorylated Cx43 at the expense of non-phosphorylated Cx43, and this change corresponded with an increase in oversized gap junction plaques. In BICR-M1R(k) cells, lactacystin treatment partially prevented the BFA-induced loss of gap junctions. Together, our data suggests that lysosomes play a key role in not only degrading internalized gap junction in BICR-M1R(k) cells but also in degrading Cx43 delivered from early secretory compartments to lysosomes in MDA-MB-231 cells. Overall proteasomal degradation regulates the stability of phosphorylated Cx43 and appears to promote the internalization of Cx43 from the cell surface.
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