The Related Roles of a Ubiquitin Processing Protease, Nutrient Sensor, and Cytidine Deaminase in the Growth‐to‐Development Transition of Dictyostelium Development

Abstract

The ubiquitin processing protease, UbpA (a homolog of yeast Ubp14 and human IsoT/USP5), is required for the growth‐to‐development transition of Dictyostelium. To understand the role of UbpA in regulating this transition, ubpA− cells were used to elucidate UbpA‐dependent pathways. ubpA− cells were hypersensitive to oxidative and nitrosative stresses, and miss‐regulated genes at the growth‐to‐development transition, including lmcB. ubpA is required for growth‐stage expression of lmcB which is involved in sensing nutrient levels and signaling cells to develop upon starvation. Exogenous expression of ubpA in ubpA− cells restored lmcB transcript levels, while exogenous expression of lmcB partially restored the developmental defect in ubpA− cells. Interestingly, lmcB is downregulated in wild‐type cells once the growth‐to‐development transition has occurred. Pull down experiments utilizing His‐tagged LmcB and TAP‐tagged LmcB expressed in Dictyostelium identified putative interacting proteins that included LmcA, PsmC5, CdaA, and a cAMP‐inducible protein. Direct binding experiments confirmed the interaction between LmcB and LmcA, and between LmcB and CdaA, a cytidine deaminase. To investigate cytidine deaminase (CDA) activity levels at the growth‐to‐development transition, a CDA assay was adapted for Dictyostelium. Wild‐type cells showed relatively low levels of CDA activity when growing and substantially increased levels upon starvation. Both growing and starving ubpA− cells have high CDA levels similar to the starving wild type cells. It is possible that LmcB binds CdaA to repress CDA activity during growth; then, upon starvation, LmcB is downregulated releasing CdaA. These results will lead to a better understanding of the mechanisms cells use to sense starvation stress and respond by making the transition from growth to development.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.