Small Heat Shock Proteins Are Novel Common Determinants of Alcohol and Nicotine Sensitivity inCaenorhabditis elegans

Abstract

Addiction to drugs is strongly determined by multiple genetic factors. Alcohol and nicotine produce distinct pharmacological effects within the nervous system through discrete molecular targets; yet, data from family and twin analyses support the existence of common genetic factors for addiction in general. The mechanisms underlying addiction, however, are poorly described and common genetic factors for alcohol and nicotine remain unidentified. We investigated the role that the heat shock transcription factor, HSF-1, and its downstream effectors played as common genetic modulators of sensitivity to addictive substances. Using Caenorhabditis elegans, an exemplary model organism with substance dose-dependent responses similar to mammals, we demonstrate that HSF-1 altered sensitivity to both alcohol and nicotine. Using a combination of a targeted RNAi screen of downstream factors and transgenic approaches we identified that these effects were contingent upon the constitutive neuronal expression of HSP-16.48, a small heat shock protein (HSP) homolog of human α-crystallin. Furthermore we demonstrated that the function of HSP-16.48 in drug sensitivity surprisingly was independent of chaperone activity during the heat shock stress response. Instead we identified a distinct domain within the N-terminal region of the HSP-16.48 protein that specified its function in comparison to related small HSPs. Our findings establish and characterize a novel genetic determinant underlying sensitivity to diverse addictive substances.

Ethanol Stimulates Locomotion via a Gαs-Signaling Pathway in IL2 Neurons inCaenorhabditis elegans

“…RNAi experiments were performed using the rrf-3 ( pk1426 ) strain. RNAi was induced by feeding ( Kamath and Ahringer 2003 ) using the ORFeome-based RNAi library ( Rual et al 2004 ) as described previously ( Johnson et al 2016 ). HT115 RNAi bacteria were cultured in LB media with 100 μg/ml ampicillin and spotted onto 60 mm diameter NGM plates supplemented with 1 mM isopropyl β-1-thiogalactopyranoside and 25 μg/ml carbenicillin.…”

“…In Drosophila , studies of acute ethanol intoxication have implicated a large number of proteins and signaling pathways ( Kaun et al 2012 ). In Caenorhabditis elegans , proteins such as Munc18 and Rab3 ( Kapfhamer et al 2008 ; Graham et al 2009 ; Johnson et al 2013 ), the BK channel slo-1 ( Davies et al 2003 ), the leak channel regulator Lightweight ( Speca et al 2010 ), chloride intracellular channels ( Bhandari et al 2012 ), and the α-crystallin ortholog HSP-16.48 ( Johnson et al 2016 ) all affect sensitivity to high levels of ethanol (400 mM). The use of very high external ethanol in C. elegans behavioral analysis is thought to be a consequence of poor penetration through the nematode cuticle ( Alaimo et al 2012 ).…”

“…The use of very high external ethanol in C. elegans behavioral analysis is thought to be a consequence of poor penetration through the nematode cuticle ( Alaimo et al 2012 ). Indeed, internal concentrations in response to 400 mM external ethanol are estimated between 20 and 60 mM ( Alaimo et al 2012 ; Johnson et al 2016 ), although not all studies are in agreement ( Mitchell et al 2007 ). In addition to sedation, at lower concentrations ethanol acts as a stimulant ( Phillips and Shen 1996 ; Wolf et al 2002 ; Balino et al 2016 ).…”

“…In C. elegans , RNA interference (RNAi) or loss-of-function mutations of hsf-1 increase stress sensitivity, but also accelerate ageing ( Hsu et al 2003 ; Prahlad et al 2008 ; Baird et al 2014 ). We have recently shown that hsf-1 loss-of-function increases sensitivity to 400 mM ethanol ( Johnson et al 2016 ). This hypersensitivity was partially the result of the downstream basal expression of HSP-16.48 , an ortholog of the human small heat shock protein α-crystallin, in a process unrelated to an HSF-1 -dependent heat shock stress response.…”

The COVID-19 Puzzle

“…Folding is usually understood as the process by which a protein attains its tertiary structure. This structure is strongly dependent on environmental conditions, and also on changes in the protein's environment [6][7][8][9][10]. Cells have developed mechanisms, which prevent aggregation of improperly folded proteins whose presence may endanger each cell and, consequently, the organism as a whole.…”