Activation of envelope glycoproteins of HIV-1 and HIV-2 in lymphatic cells by subtilisin-like proteases.
Int Conf AIDS 1996 Jul 7-12; 11:5 (abstract no. We.A.151) Hallenberger S, Moulard M, Sordel M, Klenk HD, Garten W; Philipps-University Marburg, Institute of Virology, Marburg, Germany.
The envelope proteins of human immunodeficiency virus type-1 and type-2 (HIV-1, HIV-2) mediate binding to the cellular receptor and subsequent fusion of the viral envelope with the cellular membrane. Proteolytic activation of the envelope proteins which is catalyzed by host cell enzymes is crucial for their ability to induce membrane fusion and infectivity of the virus. There is evidence that members of the family of subtilisin-like endoproteases comprising the prohormon convertases furin, PC1, PC2, PC4, PACE4, PC6, and PC7 are involved in activation of HIV envelope precursors, as they are in the case of other viral envelope proteins. We examined the presence of mammalian subtilisins in natural target cells of HIV in view of their role as potentially activating enzymes. Northern blot analyses revealed that only furin- and PC7-specific mRNAs are present in natural target cells investigating primary blood cells as well as established lympho- or monocytic cell lines. Quantification of the signals showed that especially in primary blood cells furin-mRNA is more abundant than PC7-mRNA. PACE4-mRNA could only be found in the monocytic cell line TPH-1, but not in primary macrophages. No other subtilisin-specific mRNA was detectable. Using different biochemical techniques and a 125J-labelled specific inhibitor, furin was identified as an enzymatically active enzyme present in mono- or lymphocytic cell lines. Coexpression of mammalian subtilisins with the HIV envelope precursors revealed that all of these enzymes are correctly processed in these cells, but that only furin activates HIV-1 gp160 and HIV-2 gp140. The latter was also cleaved by PC1 to some extent. The role of PC7 as an potentially activating enzyme is presently investigated. These results clearly indicate that furin and PC7 are present in natural target cells of HIV as enzymatically active enzymes.
Keywords: AEGIS, HIV-2, HIV-1, Subtilisin, Endopeptidases, Subtilisins, Glycoproteins, HIV Antigens, HIV, Cell Line, Viral Envelope Proteins, Thymus Gland, furin, GP 140, Human, ICA11
