title: Glypican-1 regulates myoblast response to HGF via Met in a lipid raft-dependent mechanism: effect on migration of skeletal muscle precursor cells.
abstract: BACKGROUND
  Via the hepatocyte growth factor receptor (Met), hepatocyte growth factor (HGF) exerts key roles involving skeletal muscle development and regeneration. Heparan sulfate proteoglycans (HSPGs) are critical modulators of HGF activity, but the role of specific HSPGs in HGF regulation is poorly understood. Glypican-1 is the only HSPG expressed in myoblasts that localize in lipid raft membrane domains, controlling cell responses to extracellular stimuli. We determined if glypican-1 in these domains is necessary to stabilize the HGF-Met signaling complex and myoblast response to HGF.
  
  
  METHODS
  C2C12 myoblasts and a derived clone (C6) with low glypican-1 expression were used as an experimental model. The activation of Met, ERK1/2 and AKT in response to HGF was evaluated. The distribution of Met and its activated form in lipid raft domains, as well as its dependence on glypican-1, were characterized by sucrose density gradient fractionation in both cell types. Rescue experiments reexpressing glypican-1 or a chimeric glypican-1 fused to the transmembrane and cytoplasmic domains of mouse syndecan-1 or myoblast pretreatment with MβCD were conducted. In vitro and in vivo myoblast migration assays in response to HGF were also performed.
  
  
  RESULTS
  Glypican-1 localization in membrane raft domains was required for a maximum cell response to HGF. It stabilized Met and HGF in lipid raft domains, forming a signaling complex where the active phospho-Met receptor was concentrated. Glypican-1 also stabilized CD44 in a HGF-dependent manner. In addition, glypican-1 was required for in vitro and in vivo HGF-dependent myoblast migration.
  
  
  CONCLUSIONS
  Glypican-1 is a regulator of HGF-dependent signaling via Met in lipid raft domains.
authors: Jaime
authors: J
authors: Gutiérrez
authors: Daniel
authors: D
authors: Cabrera
authors: Centro de Regulación Celular y Patología (CRCP), Centro de Regeneración y Envejecimiento (CARE), Departamento de Biología Celular y Molecular, MIFAB, Pontificia Universidad Católica de Chile, Santiago, Chile. ebrandan@bio.puc.cl.
authors: Enrique
authors: E
authors: Brandan