Shedding of a rhinovirus minor group binding protein: evidence for a Ca(2+)-dependent process

Soluble rhinovirus minor group binding activity was found to be shed into the medium upon incubation of HeLa cells at 37 degrees C. Although substantial amounts of this protein were released, no decrease of virus binding to the cell surface was seen. When the membrane-associated receptor was stripped from the cells with trypsin, virus binding was rapidly restored from an intracellular pool even in the absence of de novo protein synthesis. The release of this 85K virus-binding activity was inhibited by metal chelators such as EDTA, EGTA or 1,10-phenanthroline. The potential involvement of a Ca(2+)-dependent protease and/or a phospholipase in this process is discussed.