The role of calcium (Ca(2+)) in cytokinesis is controversial, and the precise pathways that lead to its release during cleavage are not well understood. Ca(2+) is released from intracellular stores by binding of inositol trisphosphate (IP3) to the IP3 receptor (IP3R), yet no clear role in cytokinesis has been established for the precursor of IP3, phosphatidylinositol 4,5-bisphosphate (PIP2). Here, using transgenic flies expressing PLCdelta-PH-GFP, which specifically binds PIP2, we identify PIP2 in the plasma membrane and cleavage furrows of dividing Drosophila melanogaster spermatocytes, and we establish that this phospholipid is required for continued ingression but not for initiation of cytokinesis. In addition, by inhibiting phospholipase C, we show that PIP2 must be hydrolyzed to maintain cleavage furrow stability. Using an IP3R antagonist and a Ca(2+) chelator to examine the roles of IP3R and Ca(2+) in cytokinesis, we demonstrate that both of these factors are required for cleavage furrow stability, although Ca(2+) is dispensable for cleavage plane specification and initiation of furrowing. Strikingly, providing cells with Ca(2+) obviates the need to hydrolyze PIP2. Thus, PIP2, PIP2 hydrolysis, and Ca(2+) are required for the normal progression of cytokinesis in these cells.

Aims/hypothesis Glucagon-like peptide-1 receptor (GLP-1R) agonists improve glucose control in animals and humans with type 1 diabetes. However, there is little information on the role of the GLP-1R in the immune system. We studied the role of the GLP-1R in immune function in wild-type (WT) and nonobese diabetic (NOD) and Glp1r

Activation of the glucagon-like peptide-1 receptor (GLP-1R) is associated with expansion of beta-cell mass due to stimulation of cell proliferation and induction of antiapoptotic pathways coupled to beta-cell survival. Although the GLP-1R agonist Exenatide (exendin-4) is currently being evaluated in subjects with type 1 diabetes, there is little information available about the efficacy of GLP-1R activation for prevention of experimental type 1 diabetes. We examined the consequences of exendin-4 (Ex-4) administration (100 ng once daily and 2 microg twice daily) on diabetes onset in nonobese diabetic mice beginning at either 4 or 9 wk of age prior to the onset of diabetes. Ex-4 treatment for 26 wk (2 microg twice daily) initiated at 4 wk of age delayed the onset of diabetes (P = 0.007). Ex-4-treated mice also exhibited a significant reduction in insulitis scores, enhanced beta-cell mass, and improved glucose tolerance. Although GLP-1R mRNA transcripts were detected in spleen, thymus, and lymph nodes from nonobese diabetic mice, Ex-4 treatment was not associated with significant changes in the numbers of CD4+ or CD8+ T cells or B cells in the spleen. However, Ex-4 treatment resulted in an increase in the number of CD4+ and CD8+ T cells in the lymph nodes and a reduction in the numbers of CD4+CD25+Foxp3+ regulatory T cells in the thymus but not in lymph nodes. These findings demonstrate that sustained GLP-1R activation in the absence of concomitant immune intervention may be associated with modest but significant delay in diabetes onset in a murine model of type 1 diabetes.