Human immunodeficiency virus Tat protein induces interleukin 6 mRNA expression in human brain endothelial cells via protein kinase C- and cAMP-dependent protein kinase pathways.
The intracellular signal transduction pathways utilized by the HIV-1-derived protein, Tat, in the activation of human central nervous system-derived endothelial cells (CNS-ECs) were examined using specific enzymatic assays. Tat induced an increase in interleukin 6 (IL-6) mRNA within 1 hr of treatment. This biological effect of Tat involved activation of both protein kinase C (PK-C) and cAMP-dependent protein kinase (PK-A) in CNS-ECs. Tat at 10 ng/ml induced a sharp, transient increase in membrane PK-C activity within 30 sec of incubation, and reached maximum levels at 2 min, declining to control values within 10 min. Tat also induced a sharp increase in intracellular cAMP levels and PK-A activity in these cells, with the PK-A activity reaching a maximum at 10 min and slowly declining to control values in 4 hr of incubation. Activation of PK-A was dependent on a Tat-induced increase in membrane PK-C activity as demonstrated by calphostin C (a PK-C inhibitor) abolishing this effect. Incubation of cells with the cyclooxygenase inhibitor indomethacin did not affect Tat-induced activation of PK-A, indicating that prostacyclins are not involved in this process. Tat-induced increase in IL-6 mRNA was abolished in the presence on PK-A inhibitor H-89, demonstrating that activation of PK-A is necessary and sufficient for the increase in IL-6 production by these cells. Both the Tat-induced increase in intracellular cAMP and IL-6 mRNA levels in CNS-ECs may play a role in altering the blood-brain barrier and thereby inducing pathology often observed in AIDS dementia.
Department of Biology and Neuroscience, University of California, Riverside 92521, USA.
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Zidovetzki
J L
JL
Wang
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Chen
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Jeyaseelan
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F
Hofman
D001921:Brain / Q000166:cytology / Q000378:metabolism* / Q000821:virology*; D002478:Cells, Cultured; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D004727:Endothelium / Q000166:cytology / Q000378:metabolism / Q000821:virology; D005786:Gene Expression Regulation; D015696:Gene Products, tat / Q000378:metabolism* / Q000494:pharmacology; D006678:HIV / Q000378:metabolism* / Q000502:physiology; D006801:Humans; D015850:Interleukin-6 / Q000096:biosynthesis* / Q000235:genetics; D011493:Protein Kinase C / Q000378:metabolism*; D012333:RNA, Messenger; D015398:Signal Transduction; D054322:tat Gene Products, Human Immunodeficiency Virus
D015696:Gene Products, tat; D015850:Interleukin-6; D012333:RNA, Messenger; D054322:tat Gene Products, Human Immunodeficiency Virus; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C