LYMPHOTOXIN-INDUCED LOSS OF PLASMA-MEMBRANE PROTEIN

  • 1 January 1979
    • journal article
    • research article
    • Vol. 94  (3) , 473-482
Abstract
Lymphotoxin-sensitive [mouse fibroblast] L cells were pre-labeled with isotopically marked leucine and exposed to human .alpha.-lymphotoxin (.alpha.-LT) or control buffer. Plasma membranes were isolated from these cells, and TCA[trichloroacetic acid]-precipitable leucine was determined as a measure of membrane protein. Human .alpha.-LT caused a marked reduction of plasmalemmal protein in LT-sensitive target cells. This loss of protein was general and not restricted to specific fractions, as assessed by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis. Since purified .alpha.-LT had no detectable proteolytic activity, the effect of the lymphokine is not readily explained by direct enzymatic action on plasma-membrane protein. There was no plasma-membrane protein loss in LT-resistant target cells on exposure to .alpha.-lymphotoxin.