Regulation of CD4-p56lck-associated phosphatidylinositol 3-kinase (PI 3-kinase) and phosphatidylinositol 4-kinase (PI 4-kinase).
CD4 serves as a receptor for MHC class II antigens and as a receptor for the human immunodeficiency virus (HIV-1) viral coat protein gp120. It is coupled to the protein-tyrosine kinase p56lck, an interaction necessary for an optimal response of certain T cells to antigen. Although anti-CD4 crosslinking may increase lck activity, the effects of HIV-1 gp120 have been controversial. Activated protein-tyrosine kinases are known to associate with certain intracellular proteins possessing src-homology regions (SH-2 domains) such as phosphatidylinositol 3-kinase (PI 3-kinase). In this paper, we demonstrate that the CD4:p56lck complex associates with significant amounts of phosphatidylinositol (PI) kinase activity. High pressure liquid chromatographic (HPLC) analysis of the reaction products demonstrated the presence of phosphatidylinositol 3-phosphate (PI 3-P) and phosphatidylinositol 4-phosphate (PI 4-P), thus indicating that PI 3 and PI 4 kinases associate with CD4-p56lck. The p85 subunit of PI 3-kinase was also detected in anti-CD4 immunoprecipitates by immunoblotting with anti-p85 antiserum. Significantly, p56lck binding to CD4 appears to be necessary for the detection of lipid kinase activity associated with p56lck. Also, anti-HIV gp120 and anti-CD4 crosslinking induced a 10-15-fold increase in levels of both PI 3- and PI 4-kinase activity in anti-CD4 precipitates. Stimulation of CD4-p56lck-linked PI kinases by crosslinked HIV-1 gp120 may play a role in HIV-1-induced immune defects.
Prasad
K V
KV
Division of Tumor Immunology, Dana-Farber Cancer Institute, Boston 02115.
Kapeller
R
R
Janssen
O
O
Duke-Cohan
J S
JS
Repke
H
H
Cantley
L C
LC
Rudd
C E
CE
D019870:1-Phosphatidylinositol 4-Kinase; D015704:CD4 Antigens / Q000378:metabolism*; D002460:Cell Line; D003432:Cross-Linking Reagents; D015699:HIV Envelope Protein gp120 / Q000378:metabolism; D015497:HIV-1 / Q000378:metabolism; D006801:Humans; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck); D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism*; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D013601:T-Lymphocytes / Q000276:immunology / Q000378:metabolism*; D014407:Tumor Cells, Cultured
D015704:CD4 Antigens; D003432:Cross-Linking Reagents; D015699:HIV Envelope Protein gp120; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor); D019870:1-Phosphatidylinositol 4-Kinase; D011505:Protein-Tyrosine Kinases; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck)