Infection of human and swine hosts by the intestinal parasite Ascaris represents a significant public health and economic problem world-wide. The adult organism is largely anaerobic, subsisting on available carbohydrate substrates during the host-feeding cycle and mobilizing endogenous glycogen during non-feeding periods. This application proposes to investigate the biochemical mechanism by which Ascaris suum regulates glycogen synthesis. The overall goal this research is to identify specific regulatory signals which modulate glycogen synthesis and metabolism in order to provide a rational approach to parasitic chemotherapy via inhibition of the glycogen utilization processes.
The specific aims are to evaluate the role of protein phosphorylation in the regulation of Ascaris glycogen synthase activity in vitro, to correlate the phosphorylation of glycogen synthase in vitro with the observed regulation of glycogen synthase activity by environmental and homeostatic pressure in vivo, and to investigate the potential significant differences in the parasite and host regulatory signals which modulate the activity of glycogen synthase. The in vitro phosphorylation of Ascaris glycogen synthase will utilize purified rabbit muscle enzymes which have been shown to phosphorylate and inactivate glycogen synthase in mammalian muscle. The kinetics of these enzymes with the Ascaris substrate will be established. Correlation of these results with in vivo phosphorylation of glycogen synthase will make use of a muscle perfusion system developed by these investigators. The method permits a systematic variation in external metabolic signals in an attempt to correlate a physiological response with a specific biochemical event. This correlation will be utilized to provide an in depth understanding of the regulation of cellular phosphorylation and the significance of these events to the organism's survival. Collectively, the data will provide a biochemical basis for the development of agents which diminish parasite survival by selectively inhibiting key regulatory signals required for the synthesis and metabolism of depot glycogen.
