The authors showed that the loss of NFB increased the cellular polyubiquitinated levels and decreased the LC3 levels for recovery periods, suggesting the role of a transcription factor during the recovery period after the heat shock. The loss of either laforin or malin is known to result in the autophagy blockade (Aguado et al. 2010; Puri et al. 2012; Criado et al. 2012; Singh et al. 2013; Garyali et al. 2014; Jain et al. 2016). 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. == Funapide Electronic supplementary material == The online version of this article (doi: 10. 1007/s12192-016-0754-9) contains supplementary material, which is available Funapide to authorized users. Keywords: Heat shock response, Ubiquitin-proteasome system, Autophagy, Epilepsy, Post-translational modifications == Introduction == Heat shock response is characterized by the induction of heat shock proteins (HSPs) that protect cellular proteins from misfolding and aggregation. HSPs also induce the E3 ubiquitin ligases that assist in the proteasome-mediated clearance of the Funapide misfolded proteins (McDonough and Patterson2003). This conserved cellular heat shock response pathway is triggered and regulated by a master regulator, the heat shock factor 1 (HSF1), a transcription factor activated by thermal stress (Cotto and Morimoto1999). HSF1 directly regulates the transcription of genes coding for the HSPs and indirectly regulates the expression of a number of genes by transactivating other transcription factors (Anckar and Sistonen2011). Thermal stress is known to denature proteins and promote their aggregation. To clear the increased load of abnormal proteins, the heat shock response is thought to be followed by the activation of proteolytic processes such as autophagy and ubiquitin proteasomal system, suggesting a cross talk between Rabbit Polyclonal to Cytochrome P450 39A1 the heat shock response and the proteolytic processes (Dokladny et al. 2015). Indeed, there is evidence suggesting that HSF1 induces autophagy through the direct transcriptional regulation of an autophagy gene. For example , HSF1 was shown to induce the transcription ofAtg7gene critical for inducing autophagy and cell survival (Desai et al. 2013). Similarly, the overexpression of HSF1 in mouse models of Alzheimers disease led to autophagy induction (Pierce et al. 2013). A study also suggests heat shock to be a protective mechanism against neurodegeneration as it induces autophagy (Liu et al. 2010). Few reports also demonstrate the negative effect of HSF1 on proteolytic processes. For example , loss of HSF1 led to the activation of basal autophagy (Dokladny et al. 2013), and, conversely, active HSF1 was also shown to suppress the expression of LC3 under heat stress (Zhao et al. 2009). While these studies suggest a functional link between the heat shock response and the proteolytic processes, these contradictory findings also call for further studies in this direction. Lafora disease (LD) is a fatal form of a teenage onset, progressive myoclonus epilepsy, characterized by other symptoms such as ataxia, dementia, psychosis, and muscle wasting (Delgado-Escueta et al. 2001; Ganesh et al. 2006). LD patients die within about 10 years of the first epileptic episode (Serratosa et al. 2012). LD is caused due to the mutations in theEPM2Aor theNHLRC1gene, coding for the laforin protein phosphatase or the malin E3 ubiquitin ligase, respectively (Singh and Ganesh2009). One of the characteristic features of LD is the formation of polyglucosan bodies, called the Lafora bodies, in the affected tissues including the neurons (Delgado-Escueta et al. 2001; Ganesh et al. 2006). LD mouse models developed polyglucosan bodies in neurons and other tissues and displayed widespread neurodegeneration (Ganesh et al. 2002). Laforin and malin are thought to function as a complex and have been shown to play a role in proteolytic processes. These include ubiquitin-proteasome system (Mittal et al. 2007; Garyali et al. 2009) and autophagy; cells deficient for laforin or malin showed autophagy blockade (Aguado et al. 2010; Puri et al. 2012; Criado et al. 2012; Singh et al. 2013; Garyali et al. 2014). A direct role for these proteins was also shown in heat shock response; laforin and malin were shown to be required for the activation and nuclear translocation of HSF1 (Sengupta et al. 2011). Since the.