Naslov
Immunochemical characterization of two isoforms of rat liver ecto-ATPase that show an immunological and structural identity with a glycoprotein cell- adhesion molecule with Mr 105, 000

Autori
Lin, S-H. ; Čulić, Ognjen ; Flanagan, D. ; Hixon, D.C

Izvornik
Biochemical journal (London. 1984) (0264-6021) 278 (1991), 1; 155-161

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
cell CAM 105 ; cell adhesion ; ecto-ATPase

Sažetak
One of the cell-adhesion molecules (CAMs) responsible for rat hepatocyte aggregation has been described as a glycoprotein having an Mr of 105, 000 (cell-CAM105). The Mr and localization of cell-CAM105 in liver membranes are very similar to those of liver ecto-ATPase, an ATPase with its nucleotide-hydrolysing site localized on the outside of the cell membrane. The protein sequence of the ecto-ATPase has been deduced from cDNA cloning. Structural analysis of the sequence indicates that the ecto-ATPase has immunoglobulin- like domains and is a member of the immunoglobulin superfamily. Since a group of proteins in the immunoglobulin superfamily has been shown to have functions related to cell adhesion, the structural characteristics of the ecto-ATPase further led to the possibility that the ecto-ATPase may have functions related to cell adhesion. In this paper, using the cDNA for the ecto-ATPase, the anti- peptide antibodies produced against peptides derived from the ecto-ATPase cDNA sequence and monoclonal antibodies against the cell-CAM105, we present evidence of identity between cell-CAM105 and ecto-ATPase. First, in Western immunoblots, two anti-cell-CAM105 monoclonal antibodies cross- reacted with the purified ecto-ATPase. Secondly, in immunodepletion experiments, antibodies against the ecto-ATPase depleted the same protein recognized by the anti-cell-CAM105 antibodies. Thirdly, in two-dimensional gel-electrophoretic analysis, anti-peptide antibodies generated against an extracellular N-terminal peptide and the intracellular C-terminal peptides of the ecto- ATPase immunoprecipitated proteins of similar isoelectric points and Mr values to those of the cell-CAM105. Fourthly, proteins immunoprecipitated by anti-ecto-ATPase antibodies and anti-cell- CAM105 antibodies have similar V8-proteinase- digest peptide maps. Finally, monoclonal antibodies against the cell-CAM105 specifically recognized the protein expressed in COS cells transfected with the ecto-ATPase cDNA. These results indicate that the ecto-ATPase cDNA codes for a protein that is identical with the cell- CAM105. Since the ecto-ATPase has structural features of immunoglobulin domains, the identity of cell-CAM105 with ecto-ATPase leads to the conclusion that this liver CAM, similarly to neuronal CAM, is also a member of the immunoglobulin supergene family. Furthermore, immunological studies indicate that the cell- CAM105/ecto-ATPase is composed of two isoforms of different C-terminal sequences. The association of ATPase activity with cell-CAM105 raises the possibility that extracellular nucleotides may play important roles in regulating cell adhesion

Izvorni jezik
Engleski

Znanstvena područja
Biologija

POVEZANOST RADA