Aggregated DsRed-tagged Cx43 and over-expressed Cx43 are targeted to lysosomes in human breast cancer cells.
To investigate if either wild-type or aggregated Cx43 is abnormally targeted to lysosomes in human breast tumor cells, we examined the fate of DsRed-tagged Cx43 and over-expressed Cx43 in communication-deficient HBL-100 and MDA-MB-231 cells. DsRed-tagged Cx43 was assembled into gap junctions in control normal rat kidney cells that express endogenous Cx43 but not in Cx43-negative HBL-100 cells. However, when HBL-100 cells were engineered to coexpress wild-type Cx43 a population of DsRed-tagged Cx43 was rescued and assembled into gap junctions. Co-expression of wild-type Cx26 failed to rescue the assembly of DsRed-tagged Cx43 into gap junctions. Immunolocalization studies revealed that DsRed-tagged Cx43 was aggregated and partially localized to lysosomes. Interestingly, when human MDA-MB-231 breast tumor cells over-expressed wild-type Cx43, Cx43 protein primarily localized to lysosomes. Together, these studies provide evidence for Cx43 being targeted to lysosomes as a result of misfolding and aggregation, while in other cases, the delivery of wild-type Cx43 to lysosomes appears to be due to defects innate to the breast tumor cell type.
Qin
H
H
Department of Anatomy and Cell Biology, University of Western Ontario, London, Canada.
Shao
Q
Q
Belliveau
D J
DJ
Laird
D W
DW
D000818:Animals; D001943:Breast Neoplasms / Q000378:metabolism*; D002460:Cell Line; D000072259:Connexin 26; D018031:Connexin 43 / Q000235:genetics / Q000378:metabolism*; D017630:Connexins / Q000378:metabolism; D005260:Female; D049452:Green Fluorescent Proteins; D006801:Humans; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism*; D008247:Lysosomes / Q000378:metabolism*; D021381:Protein Transport / Q000502:physiology*; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism*
D018031:Connexin 43; D017630:Connexins; C000607042:GJB2 protein, human; C000607044:Gjb2 protein, rat; D008164:Luminescent Proteins; D011993:Recombinant Fusion Proteins; C413663:fluorescent protein 583; D000072259:Connexin 26; D049452:Green Fluorescent Proteins