Supplementary Materialssupplement. changed the patterns of fatty acids in phosphatidylserines and phosphatidylethanolamines. The results show the involvement of ACLS4 and ACLS3 in insulin secretion. lipid synthesis from glucose carbon occurs over a time course that coincides with insulin secretion. The enzyme patterns in pancreatic islets and pancreatic beta cell lines also support the idea Temsirolimus novel inhibtior that pancreatic beta cells are a lipogenic tissue. Pancreatic beta cells in human pancreatic islets and the insulin cell collection INS-1 Rabbit Polyclonal to NOX1 832/13 contain very high levels of enzymes needed for lipid synthesis including pyruvate carboxylase [7, 8], fatty acid synthase [1, 8] and acetyl-CoA carboxylase . Acetyl-CoA carboxylase catalyzes the formation of malonyl-CoA that cells use for fatty acid synthesis as well as possibly, in the case of the beta cell, for signaling purposes [9C11]. Of the two isoforms of acetyl-CoA carboxylase (ACC1 or ACC2)1 the one that is present in pancreatic islets of humans and rats, as well as the INS-1 832/13 insulinoma cell collection, is usually ACC1 which is the isoform found in lipogenic tissues . The knockdown of pyruvate carboxylase or fatty acid synthase in the INS-1 832/13 cell collection [7, 12] lowers numerous phospholipids and inhibits glucose-induced insulin release establishing the importance of these enzymes in insulin secretion. Modifications of beta cell lipids include alterations that impact fluidity of the plasma membrane and the membrane of the insulin secretory granules. Changes in levels of phospholipids and increases in unsaturation of fatty acid side chains in phospholipids increase the fluidity and fusion of intracellular membranes. Phosphatidylserine is usually fivefold higher in the insulin secretory granules compared to the whole beta cell . The negatively charged phosphatidylserine in the insulin secretory granule membrane facilitates its fusion with the plasma membrane by its conversation with the positively charged domains of SNARE proteins in the plasma membrane . The action of P4 ATPases (flippases) that rapidly transport phosphatidylserine across the membrane of insulin secretory granules also enhance the coupling of the insulin granule membrane with the plasma membrane thus promoting the extrusion of the insulin from your insulin secretory granules into the blood circulation . P4 ATPases are highly concentrated in insulin secretory granules of beta cells and knockdown of these enzymes inhibits insulin release in INS-1 832/13 cells and in human pancreatic islets . The role of long chain acyl CoA synthetases (ACSLs) in insulin secretion has not been extensively analyzed. ACSLs convert fatty acids into acyl-CoAs that are incorporated into triglyceride, phospholipids, and cholesterols [15, 16] and also undergo -oxidation to produce energy [17, 18]. The active molecule available for -oxidation is not fatty acid itself Temsirolimus novel inhibtior but fatty acyl-CoA ester catalyzed by ACSLs. Fatty acyl-CoA esters are involved in various cellular functions including protein transport, enzyme activation, protein acylation and cell signaling [19C27] including in vesicle fusion and membrane conversation [20, 24]. Five isozymes of ACSL (ACSL1, ACSL3, ACLS4, ACSL5, and ACSL6) are known in mammalian cells [28, 29]. The five ACSLs in mammalian Temsirolimus novel inhibtior cells are divided into two sub-families depending on amino acid sequence similarity and substrate specificity. ACSL1, ACSL5 and ACSL6 are in a sub-family preferring saturated fatty acids with broad chain length as substrates [15, 28, 29]. ACSL3 and ACSL4 are in the other sub-family preferring highly unsaturated fatty acids as substrates [30C32]. ACSL3 accepts a wider range of unsaturated fatty acids than ACSL4, which highly prefers arachidonate and eicosapentaenoate. Excluding the pancreatic islet, which has not been extensively analyzed, the tissue distribution Temsirolimus novel inhibtior of the various ACSL isozymes is as follows: ACSL1 with broad substrate specificity is usually expressed abundantly in the liver, heart, and adipose tissue in which numerous fatty acids are used for energy production and storage . ACSL3 and ACSL6 are expressed highly in brain, and the amounts of mRNA that encode these two ACSLs switch in.