Multiple tyrosine protein kinases structurally related to p56 lck are down-regulated following mitogenic stimulation of human T lymphocytes.
p56 lck is a well-characterized tyrosine protein kinase (TPK) which is thought to play a role in mitogenic signal transduction in T lymphocytes. Immunoblot analysis of human lymphocyte proteins using an antiserum cross-reactive with phosphotyrosine resulted in the detection of a 55-60 kDa protein band (presumably p56 lck) as well as several additional phosphotyrosyl proteins in lymphocyte extracts. All of these phosphotyrosyl proteins were down-regulated following mitotic stimulation. Autophosphorylation of lymphocyte microsomal fractions in the presence of [gamma-32P] ATP resulted in the labelling of p56 lck as well as other proteins of different molecular weights. Analysis of these labelled proteins by tryptic digestion resulted in strikingly similar peptide maps. The data suggest that lymphocytes may contain a family of TPKs structurally related to p56 lck. The down-regulation of the putative TPKs following mitogenic stimulation of lymphocytes with phytohaemagglutinin suggests that this family of TPKs may participate in mitotic signalling events, followed by their down-regulation.
Hall
B S
BS
Department of Haematology, Royal Free Hospital and School of Medicine, London, UK.
Hoffbrand
A V
AV
Wickremasinghe
R G
RG
D015536:Down-Regulation; D006801:Humans; D066298:In Vitro Techniques; D007527:Isoenzymes / Q000378:metabolism*; D008213:Lymphocyte Activation / Q000502:physiology*; D010449:Peptide Mapping; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D015398:Signal Transduction; D013601:T-Lymphocytes / Q000201:enzymology*
D007527:Isoenzymes; D011505:Protein-Tyrosine Kinases