Mahmud, Siraje et al. (2019) International Worm Meeting "Mutation in a novel P. aeruginosa acyl-CoA dehydrogenase enhances mitochondrial UPR activity and host survival during infection."

Qureshi, Mohammed Adnan, Mahmud, Siraje, Pellegrino, Mark, Sapkota, Madhab

[International Worm Meeting, 2019]

The mitochondrial unfolded protein response (UPRmt) is a cytoprotective pathway that is activated during stress to promote recovery of damaged mitochondria. The UPRmt is also transiently activated during exposure with various bacterial species including the opportunistic pathogen Pseudomonas aeruginosa. During infection, the UPRmt regulates a subset of genes involved in innate immunity to help combat pathogens that target mitochondrial function. We screened a P. aeruginosa transposon insertion mutant library in order to identify pathogen-associated pathways that could modify the activity of the UPRmt. We identified from this screen a P. aeruginosa mutant in a novel acyl-CoA dehydrogenase, FadX, that enhances the activity of the UPRmt as well as promoting increased host survival during infection. Acyl-CoA dehydrogenases are involved in the catabolism of fatty acids via beta-oxidation as well as mediating the breakdown of branched-chain amino acids. We find that the host responds by rewiring its metabolism through a transcriptional-mediated mechanism to adjust to a shift in metabolism. Ultimately, this allows for increased energy via enhanced mitochondrial function that subsequently activates the UPRmt to help maintain homeostasis of the organelle. Our data suggests a novel metabolic communication occurring between host and pathogen that promotes a host survival benefit during infection. We will present updates on the biochemical characterization of this novel acyl-CoA dehydrogenase as well the mechanistic basis of its effect on host survival during infection.

Raisa Amin, Mustafi et al. (2019) International Worm Meeting "A novel gene-diet interaction promotes mitochondrial-UPR mediated lifespan extension and host survival during infection."

Pellegrino, Mark, Sapkota, Madhab, Raisa Amin, Mustafi, Mahmud, Siraje

[International Worm Meeting, 2019]

Mitochondrial function declines with age and is associated with the accumulation of mitochondrial DNA mutations and generation of reactive oxygen species resulting in oxidative damage. Consequently, mitochondrial dysfunction can result in cellular decline and the onset of disease owing to the critical importance of this organelle. The mitochondrial unfolded protein response (UPRmt) facilitates recovery of mitochondria to restore homeostasis. The activation of the UPRmt has been associated with increased longevity as well as promoting host survival during infection. We used a forward genetics screen approach to identify novel alleles that could activate the UPRmt. From this screen, we identified mrpl-2(osa3) which contains a novel missense mutation in the C. elegans mitochondrial ribosome gene mrpl-2. Intriguingly, we have found that the activation UPRmt by mrpl-2(osa3) is at least partially dependent on their diet, whereby induction was observed using the standard E. coli strain OP50 but not when worms were fed the RNase-deficient E. coli strain HT115. Diets consisting of other E. coli strains similarly displayed specific interactions with mrpl-2(osa3). Our results show that E. coli OP50-fed mrpl-2(osa3) animals with activated UPRmt displayed an extended lifespan and had a higher rate of survival during infection with the pathogen P. aeruginosa compared to wild-type. However, there was no significant difference in survival or lifespan between wild-type and mrpl-2(osa3) animals that were fed E. coli HT115. Based on this finding, we wished to identify the metabolite(s) that might account for the effect of diet on the ability of mrpl-2(osa3) to activate the UPRmt and promote longevity. We find that supplementing the E. coli OP50 diet with vitamin B12 suppresses the UPRmt in mrpl-2(osa3) animals as well as the associated phenotypes including extended lifespan. We are now exploring in more detail the exact mechanism behind the relationship of vitamin B12 availability and the activation of the UPRmt in mrpl-2(osa3) animals.

Raisa Amin, Mustafi et al. (2021) International Worm Meeting "Whole-animal in vivo screening for small molecule inhibitors of the mitochondrial UPR"

Qureshi, Mohammed Adnan, Pellegrino, Mark, Raisa Amin, Mustafi, Dowgielewicz, Jonathan, Mahmud, Siraje

[International Worm Meeting, 2021]

Mitochondria are essential for energy production, metabolic signaling, calcium homeostasis, and other roles. Consequently, mitochondrial dysfunction is associated with several human pathologies including neurodegenerative, cardiovascular, and metabolic diseases, as well as cancer. Thus, cells use recovery mechanisms such as the mitochondrial unfolded protein response (UPRmt) to mediate mitochondrial recovery. Importantly, the UPRmt may have clinical relevance as it has been shown to play a role in cancer survival. Hence, inhibition of the UPRmt may be leveraged as an anticancer strategy with great therapeutic promise. We employed a whole-animal chemical screening approach to identify small molecule inhibitors of the UPRmt using the C. elegans UPRmt transcriptional GFP reporter strain hsp-6::GFP. We screened a library of 1280 FDA-approved drugs for their ability to inhibit hsp-6::GFP reporter expression during stress. Among the identified hits was Paroxetine (Paxil), a type of selective serotonin reuptake inhibitor (SSRI) that blocks serotonin transporters on the presynaptic membrane, thereby increasing the concentration of this neurotransmitter at the synapse. Serotonin stabilizes our mood and feelings of well-being. Thus, SSRIs are used in the treatment of depression and other mental disorders. The connection between the SSRI Paroxetine and the activity of the UPRmt, however, has not been previously reported. Consistent with suppression of the UPRmt, Paroxetine further impaired mitochondrial function during stress but had negligible effects under standard conditions. Importantly, Paroxetine did not suppress other cellular stress response pathways including the endoplasmic reticulum UPR (UPRER). In addition, Paroxetine suppressed UPRmt-associated phenotypes including extensions in lifespan and increased host survival during infection. Unexpectedly, genetically disabling the clinical target of Paroxetine, the serotonin reuptake transporter mod-5, did not suppress UPRmt. Therefore, Paroxetine likely disables UPRmt activity through an unconventional drug target.