title: Autophagic-lysosomal inhibition compromises ubiquitin-proteasome system performance in a p62 dependent manner in cardiomyocytes.
abstract: Intracellular protein degradation is primarily performed by the ubiquitin-proteasome system (UPS) and the autophagic-lysosomal pathway (ALP). The interplay between these two pathways has been rarely examined in intact animals and the mechanism underlying the interplay remains unclear. Hence, we sought to test in vivo and in vitro the impact of inhibition of the ALP on UPS proteolytic performance in cardiomyocytes and to explore the underlying mechanism. Transgenic mice ubiquitously expressing a surrogate UPS substrate (GFPdgn) were treated with bafilomycin-A1 (BFA) to inhibit the ALP. Myocardial and renal GFPdgn protein levels but not mRNA levels were increased at 24 hours but not 3 hours after the first injection of BFA. Myocardial protein abundance of key proteasome subunits and the activities of proteasomal peptidases were not discernibly altered by the treatment. In cultured neonatal rat ventricular myocytes (NRVMs), the surrogate UPS substrate GFPu and a control red fluorescence protein (RFP) were co-expressed to probe UPS performance. At 12 hours or 24 hours after ALP inhibition by 3-methyladenine (3-MA) or BFA, GFPu/RFP protein ratios and the protein half-life of GFPu were significantly increased, which is accompanied by increases in p62 proteins. Similar findings were obtained when ALP was inhibited genetically via silencing Atg7 or Rab7. ALP inhibition-induced increases in GFPu and p62 are co-localized in NRVMs. siRNA-mediated p62 knockdown prevented ALP inhibition from inducing GFPu accumulation in NRVMs. We conclude that in a p62-dependent fashion, ALP inhibition impairs cardiac UPS proteolytic performance in cardiomyocytes in vitro and in vivo.
authors: Division of Basic Biomedical Sciences, Sanford School of Medicine of the University of South Dakota, Vermillion, South Dakota, United States of America.
authors: Zongwen
authors: Z
authors: Tian
authors: Division of Basic Biomedical Sciences, Sanford School of Medicine of the University of South Dakota, Vermillion, South Dakota, United States of America.
authors: Changhua
authors: C
authors: Wang
authors: Division of Basic Biomedical Sciences, Sanford School of Medicine of the University of South Dakota, Vermillion, South Dakota, United States of America.
authors: Chengjun
authors: C
authors: Hu
authors: Division of Basic Biomedical Sciences, Sanford School of Medicine of the University of South Dakota, Vermillion, South Dakota, United States of America.
authors: Yihao
authors: Y
authors: Tian
authors: Protein Modification and Degradation Laboratory, Departments of Pathophysiology and Biochemistry, Guangzhou Medical University, Guangzhou, Guangdong, China.
authors: Jinbao
authors: J
authors: Liu
authors: Division of Basic Biomedical Sciences, Sanford School of Medicine of the University of South Dakota, Vermillion, South Dakota, United States of America.
authors: Xuejun
authors: X
authors: Wang
mesh_terms: D000225:Adenine / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D001343:Autophagy / Q000187:drug effects; D001897:Boronic Acids / Q000494:pharmacology; D000069286:Bortezomib; D006360:Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D008247:Lysosomes / Q000378:metabolism*; D051379:Mice; D008822:Mice, Transgenic; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D061988:Proteasome Inhibitors / Q000494:pharmacology; D059748:Proteolysis; D011719:Pyrazines / Q000494:pharmacology; D051381:Rats; D000071456:Sequestosome-1 Protein; D025801:Ubiquitin / Q000378:metabolism*
chemical_list: D000970:Antineoplastic Agents; D001897:Boronic Acids; D006360:Heat-Shock Proteins; D061988:Proteasome Inhibitors; D011719:Pyrazines; D000071456:Sequestosome-1 Protein; C491079:Sqstm1 protein, rat; D025801:Ubiquitin; C025946:3-methyladenine; D000069286:Bortezomib; D046988:Proteasome Endopeptidase Complex; D000225:Adenine