title: Sortilin facilitates VLDL-B100 secretion by insulin sensitive McArdle RH7777 cells.
abstract: Studies examining the relationship between cellular sortilin and VLDL-B100 secretion demonstrate inconsistent results. Current studies explore the possibility that discrepancies may be related to insulin sensitivity. McArdle RH7777 cells (McA cells) cultured under serum enriched conditions lose sensitivity to insulin. Following incubation in serum-free DMEM containing 1% BSA, McA cells become insulin responsive and demonstrate reduced apo B secretion. Current studies indicate that insulin sensitive McA cells express lower cellular sortilin that corresponds with reduction in VLDL-B100 secretion without changes in mRNA of either sortilin or apo B. When sortilin expression is further reduced by siRNA knockdown (KD), there are additional decreases in VLDL-B100 secretion. A crystal structure of human sortilin (hsortilin) identifies two binding sites on the luminal domain for the N- and C-termini of neurotensin (NT). A small organic compound (cpd984) was identified that has strong theoretical binding to the N-terminal site. Both cpd984 and NT bind hsortilin by surface plasmon resonance. In incubations with insulin sensitive McA cells, cpd984 was shown to enhance VLDL-B100 secretion at each level of sortilin KD suggesting cpd984 acted through sortilin in mediating its effect. Current results support a role for sortilin to facilitate VLDL-B100 secretion which is limited to insulin sensitive McA cells. Inconsistent reports of the relationship between VLDL-B100 secretion and sortilin in previous studies may relate to differing functions of sortilin in VLDL-B100 secretion depending upon insulin sensitivity.
authors: School of Molecular and Cellular Biology, Department of Biochemistry, University of Illinois Urbana-Champaign, Urbana, IL 61801, USA.
authors: Robert P
authors: RP
authors: Sparks
authors: Department of Chemistry, University of South Florida, Tampa, FL 33520, USA.
authors: Wayne C
authors: WC
authors: Guida
authors: Cardiovascular Research Institute, University of Rochester Medical Center, Rochester, NY 14642, USA.
authors: Mark P
authors: MP
authors: Sowden
authors: Department of Biochemistry and Biophysics, University of Rochester Medical Center, Rochester, NY 14642, USA.
authors: Jermaine L
authors: JL
authors: Jenkins
authors: School of Molecular and Cellular Biology, Department of Biochemistry, University of Illinois Urbana-Champaign, Urbana, IL 61801, USA.
authors: Matthew L
authors: ML
authors: Starr
authors: School of Molecular and Cellular Biology, Department of Biochemistry, University of Illinois Urbana-Champaign, Urbana, IL 61801, USA.
authors: Rutilio A
authors: RA
authors: Fratti
authors: Department of Pathology and Laboratory Medicine, University of Rochester Medical Center, Rochester, NY 14642, USA.
authors: Charles E
authors: CE
authors: Sparks
authors: Department of Pathology and Laboratory Medicine, University of Rochester Medical Center, Rochester, NY 14642, USA. Electronic address: Janet_Sparks@urmc.rochester.edu.
authors: Janet D
authors: JD
authors: Sparks
mesh_terms: D033942:Adaptor Proteins, Vesicular Transport / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D053299:Apolipoprotein B-100 / Q000378:metabolism*; D001665:Binding Sites; D002460:Cell Line; D055785:Gene Knockdown Techniques; D006801:Humans; D007328:Insulin / Q000378:metabolism*; D007333:Insulin Resistance; D008079:Lipoproteins, VLDL / Q000378:metabolism*; D062105:Molecular Docking Simulation; D017207:Rats, Sprague-Dawley; D000099183:Sortilin
chemical_list: D033942:Adaptor Proteins, Vesicular Transport; D053299:Apolipoprotein B-100; D007328:Insulin; D008079:Lipoproteins, VLDL; D000099183:Sortilin
keywords: Apo B; Liver; Neurotensin; Sortilin; Surface plasmon resonance; VLDL-B100