Unexpected expression of Hsp47, a replacement of one amino acid (Val 7 Leu) in the amino terminal region, in cultured human tumorigenic cell lines

SummaryBackgroundIn general, it has been stated that keratin (K) molecules are glycosylated. During biochemical studies of K subunits, we encountered a glycoprotein that does not judge K subunits.ObjectiveThis study was intended to elucidate how the above glycoprotein co-exists in the K fraction prepared from ISO-HAS (cultured angiosarcoma cell line).MethodsWe analyzed and sequenced a remarkable spot, which was shown as a glycoprotein by periodic acid Sciff's (PAS) staining, in the K fraction prepared from ISO-HAS.ResultsThe glycoprotein was identified as an N-terminal amino acid sequence covering 10 residues of the spot. A homology search showed that it was identical to that of Hsp47 (matured type), except for one amino acid (seventh amino acid: Val 7 Leu). Similar results were confirmed for four other tumorigenic cell line types. Subsequent PAS staining using the same samples after 2D-PAGE revealed no glycosylated Ks.ConclusionNo glycosylated Ks were found by PAS staining in the K fraction prepared from four tumorigenic cell line types. During K preparation from cultured human tumor cell lines, Hsps might be associated with K expression in tumor cells.