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NLM AIDSLINE

Extracellular HIV-1 Tat protein differentially activates the JNK and ERK/MAPK pathways in CD4 T cells.




 

AIDS. 1999 Sep 10;13(13):1637-45. Unique Identifier : AIDSLINE

OBJECTIVE: To investigate the intracellular signals elicited by extracellular HIV-1 Tat protein in lymphoid CD4 T cells. METHODS: CD4 Jurkat T cells were treated with a series of glutathione S-transferase (GST)-Tat fusion proteins: full-length two-exon GST-Tat (GST-Tat2E); one-exon Tat, in which the second exon of Tat was deleted (GST-Tat1E); two-exon Tat, in which the seven arginine residues have been changed to alanine residues (GST-TatArg(mut)), GST-TatdeltaN, which shows a deletion of the N-terminal 21 amino acids. The cells were either treated with soluble GST-Tat proteins or seeded on plates coated with GST-Tat proteins immobilized on plastic. At various time points, Jurkat cells were lysed and examined for c-Jun N-terminal kinase (JNK) and extracellular signal-regulated kinase/mitogen-activated protein kinase (ERK/MAPK) activity. RESULTS: Soluble and immobilized GST-Tat2E, but not GST-Tat1E, GST-TatArg(mut) and GST-TatdeltaN, activated JNK in a dose-dependent manner, induced a rapid phosphorylation of c-Jun on Ser63 and promoted the de novo synthesis of c-Jun protein. Moreover, both GST-Tat2E and GST-Tat1E also stimulated ERK/MAPK. However, the activation of JNK was maximal at concentrations of 100 nM of GST-Tat2E and was blocked by the S6-kinase inhibitor rapamycin, whereas the activation of ERK/MAPK was already maximal at 1 nM of GST-Tat2E and was enhanced by rapamycin. CONCLUSIONS: Tat-mediated activation of JNK requires the second exon of Tat, which is dispensable for the activation of ERK/MAPK. The ability to stimulate JNK and ERK/MAPK does not require Tat internalization.

JOURNAL ARTICLE CD4-Positive T-Lymphocytes/*ENZYMOLOGY Dose-Response Relationship, Drug Enzyme Activation Enzyme Inhibitors Exons Gene Products, tat/GENETICS/*PHARMACOLOGY Glutathione Transferase/GENETICS Human *HIV-1 Jurkat Cells Mitogen-Activated Protein Kinase Kinases/*METABOLISM Mitogen-Activated Protein Kinases/*METABOLISM MAP Kinase Signaling System Phosphorylation Proto-Oncogene Proteins c-jun/BIOSYNTHESIS Sirolimus/PHARMACOLOGY Support, Non-U.S. Gov't



 




Information in this article was accurate in January 30, 2000. The state of the art may have changed since the publication date. This material is designed to support, not replace, the relationship that exists between you and your doctor. Always discuss treatment options with a doctor who specializes in treating HIV.