HIV-1 Nef alters the expression of betaII and epsilon isoforms of protein kinase C and the activation of the long terminal repeat promoter in human astrocytoma cells.
In the human immunodeficiency virus type 1 (HIV-1)-infected brain, the virus does not replicate in astrocytes, but a synthesis of viral regulatory proteins occurs in these cells, leading to accumulation of Nef. As an approach to understand the effects of Nef on astrocyte functional activity, we analyzed whether intracellular Nef interferes with the expression and activation of the enzyme protein kinase C (PKC), which is an important regulator of astroglial functions and HIV-1 replication. Astrocytoma clones (U251 MG) not expressing Nef (Neo), or expressing wild-type Nef (Bru) or nonmyristoylated Nef (TH) were used to monitor the expression and activation of 10 PKC isoforms. The same clones were used to evaluate the effect of Nef on the viral long terminal repeat (LTR) promoter after activation of PKC with the phorbol ester 12-myristate 13-acetate (PMA). PKC intracellular distribution and activation were evaluated by Western blot analysis of cytosolic and membrane fractions of control and Nef-expressing clones. PMA-induced LTR activation was analyzed in clones transfected with a plasmid encoding for the CAT reporter gene controlled by the LTR promoter, by using an enzyme-linked immunosorbent assay to measure CAT expression. Nef selectively downregulated the expression and activation of betaII and epsilon PKC isoforms in astrocytoma cells. Such downregulation correlated with an inhibition of LTR activation after PMA stimulation. The myristoylation of Nef and its membrane localization were essential for these effects. These results suggest that Nef may alter astrocytic functions by interfering with PKC expression and activation and contribute to the restriction of HIV-1 replication in astrocytes.
Ambrosini
E
E
Istituto Superiore di Sanità, Rome, Italy.
Slepko
N
N
Kohleisen
B
B
Shumay
E
E
Erfle
V
V
Aloisi
F
F
Levi
G
G
D015526:AIDS Dementia Complex / Q000201:enzymology / Q000821:virology; D000215:Acylation; D001254:Astrocytoma / Q000201:enzymology / Q000473:pathology*; D001932:Brain Neoplasms / Q000201:enzymology / Q000473:pathology*; D015500:Chloramphenicol O-Acetyltransferase / Q000096:biosynthesis; D004790:Enzyme Induction / Q000187:drug effects; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D015693:Gene Products, nef / Q000737:chemistry / Q000502:physiology*; D017930:Genes, Reporter; D015497:HIV-1 / Q000502:physiology*; D006801:Humans; D007527:Isoenzymes / Q000096:biosynthesis* / Q000235:genetics; D019814:Myristic Acid / Q000378:metabolism; D009363:Neoplasm Proteins / Q000096:biosynthesis / Q000235:genetics; D009419:Nerve Tissue Proteins / Q000096:biosynthesis* / Q000235:genetics; D011401:Promoter Regions, Genetic; D011493:Protein Kinase C / Q000096:biosynthesis* / Q000235:genetics; D064546:Protein Kinase C beta; D051744:Protein Kinase C-epsilon; D011499:Protein Processing, Post-Translational; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D020079:Terminal Repeat Sequences; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014162:Transfection; D014407:Tumor Cells, Cultured / Q000187:drug effects; D014779:Virus Replication; D054311:nef Gene Products, Human Immunodeficiency Virus
D015693:Gene Products, nef; D007527:Isoenzymes; D009363:Neoplasm Proteins; D009419:Nerve Tissue Proteins; D011993:Recombinant Fusion Proteins; D054311:nef Gene Products, Human Immunodeficiency Virus; D019814:Myristic Acid; D015500:Chloramphenicol O-Acetyltransferase; C497255:PRKCE protein, human; D011493:Protein Kinase C; D064546:Protein Kinase C beta; D051744:Protein Kinase C-epsilon; D013755:Tetradecanoylphorbol Acetate