Comparison of membrane-associated proteins of murine cytolytic and helper cloned T-cell lines: identification of a protein, p24, prominent in membrane fractions from cytolytic but not helper T-cells.
It has recently been reported that liposomes containing membrane components from cytolytic T-cell (TC) clones could transfer lytic activity to noncytolytic T- and B-cell lines, strongly suggesting that TC possess membrane-associated molecules which noncytolytic lymphocytes lack and which play a critical role in the lytic mechanism. It was thus of interest to compare the membrane-associated proteins from TC-lines to those of noncytolytic helper T-cell (TH) lines to determine whether any membrane-associated proteins unique to TC could be identified. Cells from three TC-lines and four TH-lines were internally labelled with [35S]methionine and then disrupted by hypotonic lysis. Low-density (plasma membrane enriched) and high-density (endoplasmic reticulum enriched) membrane fractions were isolated from each cloned cell line and analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis under reducing conditions. Two proteins were identified which were prominent in the membrane fractions from each of the three TC-lines but not in the membrane fractions from any of the four TH-lines. One of these, p215, migrated as a broad band with an apparent mol. wt of 215,000. The other, p24, migrated as a sharp band, or tightly spaced doublet, with an apparent mol. wt of 24,000. Immunoprecipitation studies using monoclonal antibodies to T200, LFA-1, Thy 1 and Lyt 2 suggested that p215 was a variant of T200 found on TC-lines but not on TH-lines. Treatment of solubilized membrane proteins from TH-lines with anti-T200 precipitated a 185-kD protein seen on each of the TH-lines but on none of the TC-lines. In contrast, p24 was not precipitated by any of these monoclonal antibodies. It therefore appears that p24 represents a previously unidentified protein which is strongly expressed by TC but not by TH and is thus deserving of further study as to its functional significance.
Dick
M D
MD
Masuno
T
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McCarron
R M
RM
Macchi
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B
Gately
M K
MK
D000818:Animals; D002460:Cell Line; D004591:Electrophoresis, Polyacrylamide Gel; D008565:Membrane Proteins / Q000032:analysis* / Q000276:immunology; D008715:Methionine / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D008811:Mice, Inbred DBA; D008970:Molecular Weight; D011234:Precipitins / Q000032:analysis; D051381:Rats; D011917:Rats, Inbred Lew; D013462:Sulfur Radioisotopes; D013602:T-Lymphocytes, Cytotoxic / Q000032:analysis*; D006377:T-Lymphocytes, Helper-Inducer / Q000032:analysis*
D008565:Membrane Proteins; D008715:Methionine; D011234:Precipitins; D013462:Sulfur Radioisotopes; C489067:Nrsn1 protein, mouse