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Interacting partners of macrophage-secreted cathepsin B contribute to HIV-induced neuronal apoptosis.

ABSTRACT: OBJECTIVE:HIV-1 infection of macrophages increases cathepsin B secretion and induces neuronal apoptosis, but the molecular mechanism remains unclear. DESIGN:We identified macrophage-secreted cathepsin B protein interactions extracellularly and their contribution to neuronal death in vitro. METHODS:Cathepsin B was immunoprecipitated from monocyte-derived macrophage supernatants after 12 days postinfection. The cathepsin B interactome was identified by label-free tandem mass spectrometry and compared with uninfected supernatants. Proteins identified were validated by western blot. Neurons were exposed to macrophage-conditioned media in presence or absence of antibodies against cathepsin B and interacting proteins. Apoptosis was measured using TUNEL labeling. Immunohistochemistry of postmortem brain tissue samples from healthy, HIV-infected and Alzheimer's disease patients was performed to observe the ex-vivo expression of the proteins identified. RESULTS:Nine proteins co-immunoprecipitated differentially with cathepsin B between uninfected and HIV-infected macrophages. Serum amyloid P component (SAPC)-cathepsin B interaction increased in HIV-infected macrophage supernatants, while matrix metalloprotease 9 (MMP-9)-cathepsin B interaction decreased. Pre-treatment of HIV-infected macrophage-conditioned media with antibodies against cathepsin B and SAPC decreased neuronal apoptosis. The addition of MMP-9 antibodies was not neuro-protective SAPC was overexpressed in postmortem brain tissue from HIV-positive neurocognitive impaired patients compared with HIV positive with normal cognition and healthy controls, although MMP-9 expression was similar in all tissues. CONCLUSION:Inhibiting SAPC-cathepsin B interaction protects against HIV-induced neuronal death and may help to find alternative treatments for HIV-associated neurocognitive disorders.

SUBMITTER: Cantres-Rosario YM

PROVIDER: S-EPMC4636939 | biostudies-literature | 2015 Oct

REPOSITORIES: biostudies-literature

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Interacting partners of macrophage-secreted cathepsin B contribute to HIV-induced neuronal apoptosis.

Cantres-Rosario Yisel M YM Hernandez Natalia N Negron Karla K Perez-Laspiur Juliana J Leszyk John J Shaffer Scott A SA Meléndez Loyda M LM

AIDS (London, England) 20151001 16

<h4>Objective</h4>HIV-1 infection of macrophages increases cathepsin B secretion and induces neuronal apoptosis, but the molecular mechanism remains unclear.<h4>Design</h4>We identified macrophage-secreted cathepsin B protein interactions extracellularly and their contribution to neuronal death in vitro.<h4>Methods</h4>Cathepsin B was immunoprecipitated from monocyte-derived macrophage supernatants after 12 days postinfection. The cathepsin B interactome was identified by label-free tandem mass ...[more]

PMID: 26208400

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Project description:Chronic HIV infection leads to the development of cognitive impairments, designated as HIV-associated neurocognitive disorders (HAND). The secretion of soluble neurotoxic factors by HIV-infected macrophages plays a central role in the neuronal dysfunction and cell death associated with HAND. One potentially neurotoxic protein secreted by HIV-1 infected macrophages is cathepsin B. To explore the potential role of cathepsin B in neuronal cell death after HIV infection, we cultured HIV-1(ADA) infected human monocyte-derived macrophages (MDM) and assayed them for expression and activity of cathepsin B and its inhibitors, cystatins B and C. The neurotoxic activity of the secreted cathepsin B was determined by incubating cells from the neuronal cell line SK-N-SH with MDM conditioned media (MCM) from HIV-1 infected cultures. We found that HIV-1 infected MDM secreted significantly higher levels of cathepsin B than did uninfected cells. Moreover, the activity of secreted cathepsin B was significantly increased in HIV-infected MDM at the peak of viral production. Incubation of neuronal cells with supernatants from HIV-infected MDM resulted in a significant increase in the numbers of apoptotic neurons, and this increase was reversed by the addition of either the cathepsin B inhibitor CA-074 or a monoclonal antibody to cathepsin B. In situ proximity ligation assays indicated that the increased neurotoxic activity of the cathepsin B secreted by HIV-infected MDM resulted from decreased interactions between the enzyme and its inhibitors, cystatins B and C. Furthermore, preliminary in vivo studies of human post-mortem brain tissue suggested an upregulation of cathepsin B immunoreactivity in the hippocampus and basal ganglia in individuals with HAND. Our results demonstrate that HIV-1 infection upregulates cathepsin B in macrophages, increases cathepsin B activity, and reduces cystatin-cathepsin interactions, contributing to neuronal apoptosis. These findings provide new evidence for the role of cathepsin B in neuronal cell death induced by HIV-infected macrophages.

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Interacting partners of macrophage-secreted cathepsin B contribute to HIV-induced neuronal apoptosis.

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Interacting partners of macrophage-secreted cathepsin B contribute to HIV-induced neuronal apoptosis.

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