Dysfunctional tetraspanin 7 (TSP-7) in Caenorhabditis elegans promotes; increases in average life- & health-span, stress-induced survival and motility

Abstract

Caenorhabditis elegans (C. elegans) tetraspanin-7 (TSP-7) protein is an orthologue of the Human tetraspanin CD63, which has recently been shown to be a negative regulator of autophagy. In this study a mutant strain of wild-type (WT) C. elegans (tm5761) with a 352 bp deletion in the tsp-7 gene, was studied. A polyclonal antibody was raised to a peptide sequence present only in the wild-type strain (N2). This antibody cross-reacted with the protein of the correct molecular weight (MW) in the WT lysate, but not in the tm5761, confirming the absence of a functional TSP-7 in this strain. From life-span studies, the tm5761 strain had a higher average survival age of 23.3 ± 0.6, compared to 20.1 ± 0.8 days for WT, although the absolute life-span was not statistically different. This indicates that the mutant tm5761 strain has an increased physiological health-span. Survival studies undertaken at 37 °C, showed a decrease in survival levels, with complete death of the WT occurring after 3 h of exposure, whereas the tm5761 strain was more robust (i.e. 25% survival after 3 h). Sub-lethal osmotic stress caused by increased sodium chloride (NaCl) concentrations was investigated by observing stress-related motility, such as frequency of coiling and reversing. These results showed that the tm5761 strain was more motile at higher concentrations of NaCl than the WT. These findings suggest that, like CD63, TSP-7 could be acting as a negative regulator of autophagy; therefore, the tm5761 strain likely has increased basal autophagy. This would explain its; increased, mean life- and health-span, motility under stress, and improved thermotolerance.