Shedding of Gs protein (a soluble form of the viral glycoprotein) by the rabies virus-infected BHK-21 cells.

We investigated a possible mechanism of G protein shedding occurring in the rabies virus-infected BHK-21 cell cultures. Quantitative analysis showed that about 10% of the newly synthesized G proteins were shed from the cells as Gs protein, a soluble form of G protein which lacked the C-terminal anchoring region of the protein, into the culture medium. Pulse-chase experiments revealed that the release of tritium-labeled Gs proteins began soon after the synthesis, but ceased after a short time (within about 2 hr). On the other hand, the release of the virion-associated G protein began 30 to 60 min behind the start of Gs protein shedding and continued for more than 10 hr. Gs protein could not be detected in the cells by biochemical and immunological methods at the time when large amounts of Gs protein were actively being shed. With an antiserum against the C-terminal of G protein we could detect in the cell a polypeptide having a size that is seemingly the same as that which was lost from Gs protein. These results suggest that Gs proteins are generated by a proteolytic cleavage of newly synthesized G proteins, and the cleavage seems to be stopped at a certain stage of the G protein maturation.