Daniel M. Czyz, Ph.D. - US grants

Protein conformational diseases (PCDs) are characterized by a progressive loss of neuronal or muscle function due to protein misfolding and aggregation, a common feature among diseases such as Alzheimer's, Parkinson's, Huntington's, or Lou Gehrig's disease. The exact factors that influence PCDs are not known. Recent evidence suggests that bacteria may contribute to the pathogenesis of these neurodegenerative diseases. To better understand the influence of bacteria on protein homeostasis (proteostasis), we are studying the effect of bacterial colonization of the Caenorhabditis elegans gut on protein aggregation in the intestine and other tissues. In a screen of 52 of the most common human pathogenic-commensal bacteria, we found two Gram-negative species, Pseudomonas aeruginosa and Klebsiella pneumoniae, that enhanced protein aggregation in the intestine by nearly five-fold; these two strains also affect protein aggregation in the muscle. Both species are part of the normal human microbiome and are known opportunistic pathogens. An increase in the abundance of these bacteria within the human gut was previously linked with the enhanced progression of neurodegenerative diseases. Collectively, these results suggest that intestinal bacteria affect the host folding environment; however, which bacterial factors are responsible for the enhancement of aggregation remains unknown. As such, we propose to screen genome-wide mutant libraries of P. aeruginosa and K. pneumoniae for genes that will abolish the enhancement of protein aggregation upon colonization of the C. elegans intestine. Identification of bacterial genes and pathways that are responsible for disruption of host proteostasis will provide a new mechanistic understanding of host-bacteria interaction that can provide a basis for the development of prophylactics, therapeutics, and biomarkers for PCDs.

Alzheimer?s disease (AD) is a fatal neurodegenerative disorder characterized by a progressive loss of memory and cognitive function due to protein misfolding and aggregation, a common feature among protein conformational diseases (PCDs). The exact factors that influence PCDs are not known; however, recent evidence suggests that bacteria may contribute to the pathogenesis of AD and other neurodegenerative diseases. To better understand the influence of bacteria on protein homeostasis (proteostasis), we are studying the effects of bacterial colonization of the Caenorhabditis elegans gut on protein aggregation in the intestine and other tissues. In a pilot screen of over 60 strains, we identified bacteria that can either increase or decrease protein aggregation not only in the intestine but throughout other tissues, including muscle, neurons, and gonad. We found that the bacteria that suppress protein aggregation have something in common?they produce butyrate. In follow-up experiments, we demonstrated that both exogenous and endogenous butyrate suppressed bacteria- mediated protein aggregation. These results suggest that intestinal bacteria affect host proteostasis and can potentially contribute to the pathogenesis of AD. Collectively, our preliminary data reveal a possible causative role for bacteria in diseases that are characterized by protein aggregation. As such, we propose to further investigate the effect of bacteria on proteostasis using C. elegans models by: (I) determining the impact of intestinal colonization by all human microbiome bacterial isolates on host proteostasis and pathogenesis of AD, and (II) observing the effect of exogenous and endogenous butyrate on bacteria that enhance protein aggregation. Deciphering the effect that bacteria have on host proteostasis will ultimately provide a basis for the development of prophylactics, therapeutics, and biomarkers.