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Functional mosaicism of the lymphocyte plasma membrane. II. Characterization of membrane subtractions of activated thymocytes
Author(s) -
Rode Harold N.,
Mähler Bernd,
Loracher Alois,
Resch Klaus
Publication year - 1979
Publication title -
european journal of immunology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.272
H-Index - 201
eISSN - 1521-4141
pISSN - 0014-2980
DOI - 10.1002/eji.1830090511
Subject(s) - acyltransferase , affinity chromatography , membrane , biochemistry , enzyme , sepharose , biology , microsome , concanavalin a , adenylate kinase , microbiology and biotechnology , atpase , thymocyte , t cell , in vitro , immune system , immunology
Abstract Plasma membranes of thymus lymphocytes can be fractionated by affinity chromatography on concanavalin A (Con A)‐Sepharose into two major fractions: one, MF‐1, elutes freely from the affinity column, the second, MF‐2, adheres specifically to Con A‐Sepharose. The adherent fraction MF‐2 carries mitogen receptors with higher affinity and is enriched in two enzymes, (K + + Na + )‐ATPase and acyl‐CoA:lysolecithin acyltransferase (Resch, K. et al., Biochim. Biophys. Acta 1978. 511 : 176). Microsomal membranes, derived more than 85% from the plasma membrane, of mitogen‐activated calf thymocytes were fractionated by affinity chromatography into similar fractions like resting lymphocytes, i.e. into MF‐1 and MF‐2. The activities of various membrane‐bound enzymes and fatty acid incorporation into these subfractions were compared to the corresponding similar subf ractions of nonactivated thymocytes. It appeared that two enzymes which were involved in lymphocyte activation, i.e. (K + + Na + )‐ATPase and acyl‐CoA:lysolecithin acyltransferase, were enriched in the adherent fraction MF‐2 of microsomes from both normal and mitogen‐activated thymocytes and that both were activated primarily in this fraction. Adenylate cyclase was moderately enriched in the MF‐2, but was marginally activated in both fractions of membranes of mitogen‐activated cells. Alkaline p‐nitrophenyl phosphatase, Mg 2+ ‐ATPase and γ‐glutamyltransferase were more or less evenly distributed in the plasma membrane and were strongly inhibited in both fractions of membranes from mitogen‐activated cells. Although acyl‐CoA:lysolecithin acyltransferase was activated preferentially in MF‐2, it was found that isotopically labeled fatty acids incorporated into the phospholipid lecithin quickly diffused throughout the whole membrane. These results suggest that specialized areas of the plasma membrane exist around the high‐affinity mitogen receptors which initially respond to the binding of mitogens.