Sir2B, A Sirtuin Family Protein, Involves in Cell Adhesion Molecule Expression During Early Dictyostelium Development Upon Starvation

Abstract

Sirtuin involves in cellular processes to adapt to starvation in the endocrine and metabolic systems. We examined Sir2B function during early Dictyostelium development upon starvation. GFP-tagged Sir2B was expressed and the immunoreactivity was detected a punctate pattern near cell surface. Sir2B mRNA was expressed in vegetative cells and peaked at 2 h after starvation. Ectopic expression of Sir2B enhanced aggregate formation with increased expressions of cell adhesion molecules such as cadA, csaA, TgrB1, and TgrC1 at 8h compared to those in control cells. Sir2B null-mutant cells (Sir2B KO cells) were generated and they formed aggregates smaller than those of wild-type cells after 24 h. Because cell-cell adhesion affects aggregation size, cell cohesion assay of Sir2B KO cells showed cell-cell adhesion impairment at 8 and 10 h during development, and the expressions of four cell adhesion molecules were reduced in Sir2B KO cells compared to wild-type cells until 8 h after starvation. When RNAi-mediated cadA or csaA knockdown cells (cadA KD or csaA KD cells) were generated, csaA KD cells formed smaller aggregates and affected the expressions of other cell adhesion molecules to reduce, but cadA KD cells did not show to affect aggregation size and cell adhesion molecules expressions apparently. These results suggest that Sir2B is involved in csaA expression and affects other cell adhesion molecules during early development upon starvation.