title: Autophagic vacuolation induced by excess ROS generation in HABP1/p32/gC1qR overexpressing fibroblasts and its reversal by polymeric hyaluronan.
abstract: The ubiquitous hyaladherin, hyaluronan-binding protein 1 (HABP1/p32/gC1qR) upon stable overexpression in normal fibroblasts (F-HABP07) has been reported to induce mitochondrial dysfunction, growth retardation and apoptosis after 72 h of growth. HABP1 has been observed to accumulate in the mitochondria resulting in generation of excess Reactive Oxygen Species (ROS), mitochondrial Ca(++) efflux and drop in mitochondrial membrane potential. In the present study, autophagic vacuolation was detected with monodansylcadaverin (MDC) staining from 36 h to 60 h of culture period along with elevated level of ROS in F-HABP07 cells. Increased expression of autophagic markers like MAP-LC3-II, Beclin 1 and autophagic modulator, DRAM confirmed the occurrence of the phenomenon. Reduced vacuole formation was observed upon treatment with 3-MA, a known PI3 kinase inhibitor, only at 32 h and was ineffective if treated later, as high ROS level was already attained. Treatment of F111 and F-HABP07 cells with bafilomycin A1 further indicated an increase in autophagosome formation along with autophagic degradation in HABP1 overexpressed fibroblasts. Comparison between normal fibroblast (F111) and F-HABP07 cells indicate reduced level of polymeric HA, its depolymerization and perturbed HA-HABP1 interaction in F-HABP07. Interestingly, supplementation of polymeric HA, an endogenous ROS scavenger, in the culture medium prompted reduction in number of vacuoles in F-HABP07 along with drop in ROS level, implying that excess ROS generation triggers initiation of autophagic vacuole formation prior to apoptosis due to overexpression of HABP1. Thus, the phenomenon of autophagy takes place prior to apoptosis induction in the HABP1 overexpressing cell line, F-HABP07.
authors.affiliation: Biochemistry and Toxicology Laboratory, School of Environmental Sciences, Jawaharlal Nehru University, New Delhi, India.
authors.forename: Paramita
authors.initials: P
authors.lastname: Saha
authors.forename: Anindya Roy
authors.initials: AR
authors.lastname: Chowdhury
authors.forename: Shubhra
authors.initials: S
authors.lastname: Dutta
authors.forename: Soumya
authors.initials: S
authors.lastname: Chatterjee
authors.forename: Ilora
authors.initials: I
authors.lastname: Ghosh
authors.forename: Kasturi
authors.initials: K
authors.lastname: Datta
mesh_terms: D000818:Animals; D051017:Apoptosis Regulatory Proteins / Q000235:genetics / Q000378:metabolism; D001343:Autophagy / Q000187:drug effects; D000071186:Beclin-1; D005347:Fibroblasts / Q000187:drug effects* / Q000378:metabolism*; D019084:Fluorescent Antibody Technique, Indirect; D018960:Hyaluronan Receptors / Q000235:genetics / Q000378:metabolism*; D006820:Hyaluronic Acid / Q000494:pharmacology*; D015151:Immunoblotting; D007150:Immunohistochemistry; D007976:Leupeptins / Q000494:pharmacology; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D046529:Microscopy, Electron, Transmission; D024101:Mitochondrial Proteins; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism*; D014617:Vacuoles / Q000187:drug effects / Q000378:metabolism
chemical_list: D051017:Apoptosis Regulatory Proteins; D000071186:Beclin-1; C512829:Becn1 protein, rat; C490195:C1qbp protein, rat; D018960:Hyaluronan Receptors; D007976:Leupeptins; D024101:Mitochondrial Proteins; D017382:Reactive Oxygen Species; D006820:Hyaluronic Acid; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde