title: Overcoming the spatial barriers of the stimulus secretion cascade in pancreatic β-cells.
abstract: The ability of the pancreatic β-cells to adapt the rate of insulin release in accordance to changes in circulating glucose levels is essential for glucose homeostasis. Two spatial barriers imposed by the plasma membrane and inner mitochondrial membrane need to be overcome in order to achieve stringent coupling between the different steps in the stimulus-secretion cascade.   The first spatial barrier is overcome by the presence of a glucose transporter (GLUT) in the plasma membrane, whereas a low affinity hexokinase IV (glucokinase, GK) in the cytosol conveys glucose availability into a metabolic flux that triggers and accelerates insulin release. The mitochondrial inner membrane comprises a second spatial barrier that compartmentalizes glucose metabolism into glycolysis (cytosol) and tricarboxylate (TCA) cycle (mitochondrial matrix). The exchange of metabolites between cytosol and mitochondrial matrix is mediated via a set of mitochondrial carriers, including the aspartate-glutamate carrier (aralar1), α- ketoglutarate carrier (OGC), ATP/ADP carrier (AAC), glutamate carrier (GC1), dicarboxylate carrier (DIC) and citrate/isocitrate carrier (CIC). The scope of this review is to provide an overview of the role these carriers play in stimulus-secretion coupling and discuss the importance of these findings in the context of the exquisite glucose responsive state of the pancreatic β-cell.
authors.affiliation: School of Pharmacy; Health Science Campus; University of Waterloo; Kitchener, CN Canada.
authors.forename: Peter R
authors.initials: PR
authors.lastname: Huypens
authors.affiliation: School of Pharmacy; Health Science Campus; University of Waterloo; Kitchener, CN Canada.
authors.forename: Mei
authors.initials: M
authors.lastname: Huang
authors.affiliation: School of Pharmacy; Health Science Campus; University of Waterloo; Kitchener, CN Canada.
authors.forename: Jamie W
authors.initials: JW
authors.lastname: Joseph
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism; D005947:Glucose / Q000378:metabolism*; D051246:Glucose Transport Proteins, Facilitative / Q000378:metabolism*; D018698:Glutamic Acid / Q000378:metabolism; D006019:Glycolysis; D006153:Guanosine Diphosphate / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000378:metabolism; D006801:Humans; D050417:Insulin-Secreting Cells / Q000378:metabolism*; D008928:Mitochondria / Q000378:metabolism*; D033681:Mitochondrial Membrane Transport Proteins / Q000378:metabolism*; D051336:Mitochondrial Membranes / Q000378:metabolism; D009249:NADP / Q000378:metabolism
chemical_list: D051246:Glucose Transport Proteins, Facilitative; D033681:Mitochondrial Membrane Transport Proteins; D006153:Guanosine Diphosphate; D018698:Glutamic Acid; D009249:NADP; D006160:Guanosine Triphosphate; D005947:Glucose