title: Proteolysis of mature HIV-1 p6 Gag protein by the insulin-degrading enzyme (IDE) regulates virus replication in an Env-dependent manner.
abstract: There is a significantly higher risk for type II diabetes in HIV-1 carriers, albeit the molecular mechanism for this HIV-related pathology remains enigmatic. The 52 amino acid HIV-1 p6 Gag protein is synthesized as the C-terminal part of the Gag polyprotein Pr55. In this context, p6 promotes virus release by its two late (L-) domains, and facilitates the incorporation of the viral accessory protein Vpr. However, the function of p6 in its mature form, after proteolytic release from Gag, has not been investigated yet. We found that the mature p6 represents the first known viral substrate of the ubiquitously expressed cytosolic metalloendopeptidase insulin-degrading enzyme (IDE). IDE is sufficient and required for degradation of p6, and p6 is approximately 100-fold more efficiently degraded by IDE than its eponymous substrate insulin. This observation appears to be specific for HIV-1, as p6 proteins from HIV-2 and simian immunodeficiency virus, as well as the 51 amino acid p9 from equine infectious anaemia virus were insensitive to IDE degradation. The amount of virus-associated p6, as well as the efficiency of release and maturation of progeny viruses does not depend on the presence of IDE in the host cells, as it was shown by CRISPR/Cas9 edited IDE KO cells. However, HIV-1 mutants harboring IDE-insensitive p6 variants exhibit reduced virus replication capacity, a phenomenon that seems to depend on the presence of an X4-tropic Env. Furthermore, competing for IDE by exogenous insulin or inhibiting IDE by the highly specific inhibitor 6bK, also reduced virus replication. This effect could be specifically attributed to IDE since replication of HIV-1 variants coding for an IDE-insensitive p6 were inert towards IDE-inhibition. Our cumulative data support a model in which removal of p6 during viral entry is important for virus replication, at least in the case of X4 tropic HIV-1.
authors.affiliation: Institute of Virology, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany.
authors.forename: Friedrich
authors.initials: F
authors.lastname: Hahn
authors.affiliation: Institute of Virology, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany.
authors.forename: Adrian
authors.identifier: http://orcid.org/0000-0003-2462-2675
authors.initials: A
authors.lastname: Schmalen
authors.affiliation: Institute of Virology, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Setz
authors.affiliation: Institute of Virology, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany.
authors.forename: Melanie
authors.initials: M
authors.lastname: Friedrich
authors.affiliation: Institute of Virology, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Schlößer
authors.affiliation: Institute of Virology, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany.
authors.forename: Julia
authors.initials: J
authors.lastname: Kölle
authors.affiliation: Institute of Virology, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany.
authors.forename: Robert
authors.initials: R
authors.lastname: Spranger
authors.affiliation: Institute of Virology, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany.
authors.forename: Pia
authors.initials: P
authors.lastname: Rauch
authors.affiliation: Institute of Virology, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany.
authors.forename: Kirsten
authors.identifier: http://orcid.org/0000-0003-4792-4991
authors.initials: K
authors.lastname: Fraedrich
authors.affiliation: Institute of Virology, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany.
authors.forename: Tatjana
authors.initials: T
authors.lastname: Reif
authors.affiliation: Institute of Virology, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany.
authors.forename: Julia
authors.initials: J
authors.lastname: Karius-Fischer
authors.affiliation: Translational Metabolism Unit, Diabetes Research Center, Division of Diabetes, Endocrinology and Metabolism, Baylor College of Medicine, Houston, Texas, United States of America.
authors.forename: Ashok
authors.initials: A
authors.lastname: Balasubramanyam
authors.affiliation: Institute of Biochemistry, Charité Universitätsmedizin-Berlin, Berlin, Germany.
authors.forename: Petra
authors.initials: P
authors.lastname: Henklein
authors.affiliation: Department of Chemistry and Centre for Pharmacy, University of Bergen, Bergen, Norway.
authors.forename: Torgils
authors.initials: T
authors.lastname: Fossen
authors.affiliation: Institute of Virology, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Schubert
mesh_terms: D002478:Cells, Cultured; D015686:Gene Products, env / Q000378:metabolism*; D015497:HIV-1 / Q000502:physiology*; D006367:HeLa Cells; D006801:Humans; D007328:Insulin / Q000378:metabolism; D007339:Insulysin / Q000378:metabolism*; D059748:Proteolysis; D013601:T-Lymphocytes / Q000378:metabolism; D014779:Virus Replication; D054301:gag Gene Products, Human Immunodeficiency Virus / Q000378:metabolism*
chemical_list: D015686:Gene Products, env; D007328:Insulin; D054301:gag Gene Products, Human Immunodeficiency Virus; C083002:p6 gag protein, Human immunodeficiency virus 1; D007339:Insulysin