Powerful Strategy That Is Definitely Assisting All Ion Channel Ligand Library Fans

, 2010). This SNP replaces a neutral glycine (G388) with a charged arginine (R388) in the transmembrane domain, a general hot spot in receptor tyrosine kinases for disease-related sequence variations; however, its mechanism of action remains unclear. Here we show that this cancer-associated FGFR4 variant signals in a tissue-specific manner to enhance pancreatic insulin secretion. While multiple FGFRs, including FGFR4, are expressed in adult pancreatic islets ( Oberg-Welsh and Welsh, Ion Channel Ligand Library cost 1996; Hughes, 1997; Le Bras et?al., 1998; Dichmann et?al., 2003; Takaishi et?al., 2000), their actions in modulating beta islet cell signaling and physiologic functions remain unclear. To specifically examine functional differences between prototypic FGFR4 (FGFR4-G388) and the cancer-associated FGFR4-R388 variant, we initially expressed these isoforms in pancreatic islet RINm5F cells that endogenously express FGFR4 and its coreceptor, klotho beta (KLB). Cells were stimulated with FGF1, which stimulates all FGFR isotypes, the FGFR2-selective ligand FGF7, or the FGFR4-selective ligand FGF19. FGFR responses confirmed the anticipated activation of the immediate FGFR substrate 2 (FRS2) and pErk1/2 MAPK in wild-type RINm5F cells ( Figure?S1A available online). Cells expressing FGFR4-G388 similarly exhibited the predicted FGFR signaling responses ( Figure?1A). In contrast, PIK-3 FGFR4-R388-expressing cells failed to activate FRS2 in response to FGF stimulation. Nevertheless, FGFR4-R388-expressing islet cells secreted nearly twice as much insulin as cells expressing the wild-type (FGFR4-G388) receptor (p?www.selleckchem.com/products/E7080.html activity; electron microscopy revealed that islet cells expressing FGFR4-G388 had well-developed rough endoplasmic reticulum, large Golgi complexes, and numerous secretory granules ( Figure?1C), whereas islet cells expressing FGFR4-R388 had evidence of active synthesis but very few stored secretory granules, consistent with increased secretion ( Figure?1C). The increased insulin secretion by FGFR4-R388 cells was sensitive to diazoxide inhibition but not to enhancement by tolbutamide treatment ( Figure?S1B). Additionally, expression of glucose-sensing genes including hexokinase 1 (HK1) and K+ATP channel subunits, KCNJ11, KCNJ15, and ABCC8 were not measurably influenced by the two FGFR4 isoforms (data not shown). To identify genes involved in the divergent signaling and actions displayed by the FGFR4 isoforms, we performed microarray gene expression profiling comparing pancreatic insulin-producing cells expressing empty vector, FGFR4-G388, or FGFR4-R388. We sought to identify a target that can potentially attenuate wild-type FGFR signaling by FGFR4-R388 ( Table S1). This candidate proved to be the adaptor protein Grb14 (accession number NM_03162) as determined by quantitative real-time PCR and western blotting.