title: 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.
  
  
  METHODS
  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.
  
  
  CONCLUSIONS
  Inhibiting SAPC-cathepsin B interaction protects against HIV-induced neuronal death and may help to find alternative treatments for HIV-associated neurocognitive disorders.
authors.affiliation: aUniversity of Puerto Rico, Medical Sciences Campus, Department of Microbiology and Medical Zoology bUniversity of Puerto Rico, Rio Piedras Campus, Department of Biology, San Juan cUniversity of Puerto Rico, Bayamón Campus, Department of Biology, Bayamón dUniversity of Puerto Rico, Medical Sciences Campus, RCMI Translational Proteomics Center, San Juan, Puerto Rico eProteomics and Mass Spectrometry Facility and Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts, USA.
authors.forename: Yisel M
authors.initials: YM
authors.lastname: Cantres-Rosario
authors.forename: Natalia
authors.initials: N
authors.lastname: Hernandez
authors.forename: Karla
authors.initials: K
authors.lastname: Negron
authors.forename: Juliana
authors.initials: J
authors.lastname: Perez-Laspiur
authors.forename: John
authors.initials: J
authors.lastname: Leszyk
authors.forename: Scott A
authors.initials: SA
authors.lastname: Shaffer
authors.forename: Loyda M
authors.initials: LM
authors.lastname: Meléndez
mesh_terms: D017209:Apoptosis; D002401:Cathepsin B / Q000378:metabolism*; D002478:Cells, Cultured; D017077:Culture Media, Conditioned; D005260:Female; D015658:HIV Infections / Q000276:immunology* / Q000473:pathology / Q000821:virology; D015497:HIV-1 / Q000276:immunology*; D006801:Humans; D008264:Macrophages / Q000276:immunology* / Q000821:virology*; D009474:Neurons / Q000187:drug effects* / Q000502:physiology
chemical_list: D017077:Culture Media, Conditioned; D002401:Cathepsin B