title: Loss of malin, but not laforin, results in compromised autophagic flux and proteasomal dysfunction in cells exposed to heat shock.
abstract: Heat stress to a cell leads to the activation of heat shock response, which is required for the management of misfolded and unfolded proteins. Macroautophagy and proteasome-mediated degradation are the two cellular processes that degrade polyubiquitinated, misfolded proteins. Contrasting pieces of evidence exist on the effect of heat stress on the activation of the above-mentioned degradative pathways. Laforin phosphatase and malin E3 ubiquitin ligase, the two proteins defective in Lafora neurodegenerative disorder, are involved in cellular stress response pathways and are required for the activation of heat shock transcription factor - the heat shock factor 1 (HSF1) - and, consequently, for cellular protection under heat shock. While the role of laforin and malin in the proteolytic pathways is well established, their role in cellular recovery from heat shock was not explored. To address this, we investigated autophagic flux, proteasomal activity, and the level of polyubiquitinated proteins in Neuro2a cells partially silenced for laforin or malin protein and exposed to heat shock. We found that heat shock was able to induce autophagic flux, proteasomal activity and reduce the polyubiquitinated proteins load in the laforin-silenced cells but not in the malin-deficient cells. Loss of malin leads to reduced proteasomal activity in the heat-shocked cells. Taken together, our results suggest a distinct mode of action for laforin and malin in the heat shock-induced proteolytic processes.
authors.affiliation: Department of Biological Sciences and Bioengineering, Indian Institute of Technology, Kanpur, 208016, India.
authors.forename: Navodita
authors.initials: N
authors.lastname: Jain
authors.affiliation: Department of Biological Sciences and Bioengineering, Indian Institute of Technology, Kanpur, 208016, India.
authors.forename: Anupama
authors.initials: A
authors.lastname: Rai
authors.affiliation: Department of Biological Sciences and Bioengineering, Indian Institute of Technology, Kanpur, 208016, India.
authors.forename: Rohit
authors.initials: R
authors.lastname: Mishra
authors.affiliation: Department of Biological Sciences and Bioengineering, Indian Institute of Technology, Kanpur, 208016, India. sganesh@iitk.ac.in.
authors.forename: Subramaniam
authors.identifier: 0000-0002-9908-9177
authors.initials: S
authors.lastname: Ganesh
mesh_terms: D000818:Animals; D001343:Autophagy; D045744:Cell Line, Tumor; D054637:Dual-Specificity Phosphatases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D000076249:Heat Shock Transcription Factors / Q000378:metabolism; D018869:Heat-Shock Response / Q000502:physiology*; D007976:Leupeptins / Q000494:pharmacology; D018942:Macrolides / Q000633:toxicity; D051379:Mice; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex / Q000737:chemistry / Q000378:metabolism*; D054558:Protein Tyrosine Phosphatases, Non-Receptor; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism; D013696:Temperature; D044767:Ubiquitin-Protein Ligases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D054875:Ubiquitination
chemical_list: D000076249:Heat Shock Transcription Factors; D007976:Leupeptins; D018942:Macrolides; C480860:Map1lc3b protein, mouse; D008869:Microtubule-Associated Proteins; D034741:RNA, Small Interfering; C040929:bafilomycin A1; C572596:NHLRC1 protein, mouse; D044767:Ubiquitin-Protein Ligases; D054637:Dual-Specificity Phosphatases; C491989:Epm2a protein, mouse; D054558:Protein Tyrosine Phosphatases, Non-Receptor; D046988:Proteasome Endopeptidase Complex; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde
keywords: Autophagy; Epilepsy; Heat shock response; Post-translational modifications; Ubiquitin-proteasome system