Journal of Cell Science, Vol 21, Issue 2 407-413, Copyright © 1976 by Company of Biologists

JOURNAL ARTICLES

Neutral protease activity of Rous sarcoma (RSV) transformed chick embryo fibroblasts

AC Spataro, HR Morgan and HB Bosmann

The proteolytic activities of normal, Schmidt-Ruppin Rous sarcoma virus (SR-RSV) transformed, and infected (RAV) chick embryo fibroblasts (CEF) have been measured by a highly sensitive technique using 3H-acetylated haemoglobin as a substrate.When all 3 types of CEF cells were maintained in serumless media, no differences were detected in the amount of pH 3-4 protease activity released into the media over a 24-h period, and only negligible amounts of pH 7-6 proteolytic activity were found. When normal, transformed, and infected cells were maintained in serumless media and later incubated with 3H-acetylate haemoglobin, a significant proteolysis of the haemoglobin, a 6-fold increase compared to the normal CEF cells, was associated only with plates containing SR-RSV-CEF cells. A fluorescent assay for peptides confirmed that SR-RSV-CEF cells have increased cell-associated proteolytic activity. The net surface charge of the transformed CEF cells was unchanged by maintenance in serumless media but the net surface negativity of the normal and RAV-CEF cells was significantly increased by incubation in media minus serum for 24 h. This suggests that normal CEF cells, maintained in media plus serum, have a substance masking their surface charge which is absent from the surface of transformed cells, possibly because of proteolytic degradation.