Ywhaz/14-3-3zeta deletion improves glucose tolerance through a GLP-1-dependent mechanism

Multiple signaling pathways mediate the actions of metabolic hormones to control glucose homeostasis, but the proteins that coordinate such networks are poorly understood. We previously identified the molecular scaffold protein, 14-3-3ζ, as a critical regulator of in vitro β-cell survival and adipogenesis, but its metabolic roles in glucose homeostasis have not been studied in depth. Herein, we report that Ywhaz gene knockout mice (14-3-3ζKO) exhibited elevated fasting insulin levels while maintaining normal β-cell responsiveness to glucose when compared with wild-type littermate controls. In contrast with our observations after an ip glucose bolus, glucose tolerance was significantly improved in 14-3-3ζKO mice after an oral glucose gavage. This improvement in glucose tolerance was associated with significantly elevated fasting glucagon-like peptide-1 (GLP-1) levels. 14-3-3ζ knockdown in GLUTag L cells elevated GLP-1 synthesis and increased GLP-1 release. Systemic inhibition of the GLP-1 receptor attenuated the improvement in oral glucose tolerance that was seen in 14-3-3ζKO mice. When taken together these findings demonstrate novel roles of 14-3-3ζ in the regulation of glucose homeostasis and suggest that modulating 14-3-3ζ levels in intestinal L cells may have beneficial metabolic effects through GLP-1-dependent mechanisms. Multiple cell types secrete hormones that act in concert to ensure the rapid clearance of circulating glucose following the ingestion of nutrients. For example, insulin is released from pancreatic β-cells to promote glucose uptake in skeletal muscle and adipose tissue, and to reduce hepatic gluconeogenesis. The incretin hormones, glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic peptide (GIP), are secreted from intestinal endocrine L-cells and K-cells, respectively, whereby they potentiate glucose-induced insulin secretion from β-cells and delay gastric emptying (1). Within cell types relevant for glucose homeostasis, it is unclear how complex signaling networks are accurately coordinated. Molecular scaffold proteins coordinate signaling events by regulating protein subcellular localization, promoting protein stability, and nucleating macromolecular complexes (2, 3). Their interactions with target proteins are dependent on their recognition of specific motifs that are unique to each scaffold (3, 4). Despite their essential functions in coordinating signaling networks, only a few scaffold proteins have been investigated for their roles in glucose homeostasis. For example, β-arrestins, Akap150, and NLRP3 have been shown to be important in pancreatic β-cell function, glucose homeostasis, and adipogenesis (5–10). However, these examples represent a small fraction of identified scaffold proteins, and the role of other proteins families in glucose homeostasis remain understudied. The seven-member family of molecular scaffolds called 14-3-3 proteins is highly conserved and broadly expressed in metabolically relevant tissues. 14-3-3 proteins are known to bind to several insulin signaling proteins that are required for glucose metabolism and β-cell function, including Irs1, Irs2, Raf1, Foxo1, and As160/TBD1C4 (11–19). Members of the 14-3-3 family have also been shown to participate in the regulation of hormone and neurotransmitter exocytosis (20–22), which is particularly relevant to glucose homeostasis control (23, 24). We have demonstrated that the 14-3-3ζ isoform (encoded by the Ywhaz gene) has unique and critical roles in the regulation of β-cell survival and adipocyte differentiation (25, 26). Together with other studies, our recent findings prompted us to test the hypothesis that modulating 14-3-3ζ levels affects whole-body glucose homeostasis and metabolism. In the present study, we report that 14-3-3ζ deletion improves oral glucose tolerance in association with increased basal GLP-1 secretion from intestinal L cells. Modulating 14-3-3ζ expression in the intestine could potentially serve as a therapeutic approach to increase circulating GLP-1 levels and to improve glucose homeostasis. - See more at: http://press.endocrine.org/doi/10.1210/en.2016-1016#sthash.Lck6f8YR.dpufGareth E. Lim, Micah Piske, James E. Lulo, Hayley S. Ramshaw, Angel F. Lopez, and James D. Johnso

High CD123 levels enhance proliferation in response to IL-3, but reduce chemotaxis by downregulating CXCR4 expression

High expression of the α chain of the interleukin-3 receptor (IL-3Rα; CD123) is a hallmark of acute myeloid leukemia (AML) leukemic stem cells (LSCs). Elevated CD123 expression is part of the diagnostic immunophenotyping of myeloid leukemia, and higher expression is associated with poor prognosis. However, the biological basis of the poorer prognosis is unclear, and may include heightened IL-3 signaling and non-cell autonomous interactions with the bone marrow (BM) microenvironment. We used TF-1 cells expressing different levels of CD123 and found elevated CD123 levels amplified the proliferative response to exogenous IL-3 and maintained viability in reducing IL-3 concentrations. This was associated with stronger activation of STAT5, Akt, and extracellular signal-regulated kinase 1/2 in vitro. Surprisingly, in vivo e14.5 fetal liver cells transduced with retroviral constructs to express high CD123 failed to engraft in syngeneic recipients. In exploring the underlying mechanism for this, we found that CXCR4, a key molecule involved in LSC/BM interactions, was specifically downregulated in CD123 overexpressing cells in a manner dependent on IL-3 signaling. CXCR4 downregulation was sufficient to alter the chemotactic response of hematopoietic cells to stromal derived factor-1 (SDF-1). Thus, we propose that the overexpression of CD123 in AML LSC dictates their location by altering CXCR4/SDF-1 interaction in the BM, raising the possibility that this mechanism underpins the egress of BM AML LSC and more mature cells into the circulation.Nicole L. Wittwer ... Melanie K. Pudney, Mara Dottore, Richard J. D’Andrea, Angel F. Lopez ... Hayley S. Ramshaw ... et al

Targeting the human βc Receptor inhibits contact dermatitis in a transgenic mouse model

Allergic contact dermatitis (ACD) is a prevalent and poorly controlled inflammatory disease caused by skin infiltration of T cells and granulocytes. The beta common (bc) cytokines GM-CSF, IL-3, and IL-5 are powerful regulators of granulocyte function that signal through their common receptor subunit bc, a property that has made bc an attractive target to simultaneously inhibit these cytokines. However, the species specificity of bc has precluded testing of inhibitors of human bc in mouse models. To overcome this problem, we developed a human bc receptor transgenic mouse strain with a hematopoietic cell‒specific expression of human bc instead of mouse bc. Human bc receptor transgenic cells responded to mouse GM-CSF and IL-5 but not to IL-3 in vitro and developed tissue pathology and cellular inflammation comparable with those in wild-type mice in a model of ACD. Similarly, Il3e/e mice developed ACD pathology comparable with that of wild-type mice. Importantly, the blocking antiehuman bc antibody CSL311 strongly suppressed ear pinna thickening and histopathological changes typical of ACD and reduced accumulation of neutrophils, mast cells, and eosinophils in the skin. These results show that GM-CSF and IL-5 but not IL-3 are major mediators of ACD and define the human bc receptor transgenic mouse as a unique platform to test the inhibitors of bc in vivo.Kwok Ho Yip ... Barbara J. McClure ... Angel F. Lopez ... Harshita Pant ... Hayley S. Ramshaw ... et. a

MicroRNA-194 promotes prostate cancer metastasis by inhibiting SOCS2

Abstract not availableRajdeep Das, Philip A. Gregory, Rayzel C. Fernandes, Iza Denis, Qingqing Wang, Scott L. Townley, Shuang G. Zhao, Adrienne R. Hanson, Marie A. Pickering, Heather K. Armstrong, Noor A. Lokman, Esmaeil Ebrahimie, Elai Davicioni, Robert B. Jenkins, R. Jeffrey Karnes, Ashley E. Ross, Robert B. Den, Eric A. Klein, Kim N. Chi, Hayley S. Ramshaw, Elizabeth D. Williams, Amina Zoubeidi, Gregory J. Goodall, Felix Y. Feng, Lisa M. Butler, Wayne D. Tilley, and Luke A. Selt