PREVALENCE OF THE MERCURIAL-SENSITIVE ECTOATPASE IN HUMAN SMALL-CELL LUNG-CARCINOMA - CHARACTERIZATION AND PARTIAL-PURIFICATION

Cell surface ATPase (ectoATPase) activity is detected on many mammalia n cells. Previous documentation in the rat hepatocyte-hepatoma system indicated that ectoATPase activity increased during tumorigenesis with accompanying changes in enzymatic properties and localization. These results, combined with the recently established characteristics of two distinct ectoATPases, a mercurial-sensitive ectoATPase, and a mercuri al-insensitive ectoATPase, suggest that the former is increased, where as the latter is decreased, during hepatoma formation. We found that t he mercurial-sensitive ectoATPase was also expressed at high levels in three lines of human small cell lung carcinoma (SCLC) cells. During p urification of this enzyme from an SCLC xenograft, four isoforms of th is enzyme, with similar biochemical properties but different ionic cha rges were detected. The elution of two proteins of 170 and 150 kDa fro m a DEAE-cellulose column appeared to correlate with elution of ATPase activity. These characterizations should be useful in the further inv estigation of the molecular structure and function of the SCLC mercuri al-sensitive ectoATPase which may be an important cell surface marker of SCLC cells. (C) 1994 Academic Press, Inc.