Lysosomal trafficking of TGFBIp via caveolae-mediated endocytosis

PLoS One. 2015 Apr 8;10(4):e0119561. doi: 10.1371/journal.pone.0119561. eCollection 2015.

Abstract

Transforming growth factor-beta-induced protein (TGFBIp) is ubiquitously expressed in the extracellular matrix (ECM) of various tissues and cell lines. Progressive accumulation of mutant TGFBIp is directly involved in the pathogenesis of TGFBI-linked corneal dystrophy. Recent studies reported that mutant TGFBIp accumulates in cells; however, the trafficking of TGFBIp is poorly understood. Therefore, we investigated TGFBIp trafficking to determine the route of its internalization and secretion and to elucidate its roles in the pathogenesis of granular corneal dystrophy type 2 (GCD2). Our data indicate that newly synthesized TGFBIp was secreted via the endoplasmic reticulum/Golgi-dependent secretory pathway, and this secretion was delayed in the corneal fibroblasts of patients with GCD2. We also found that TGFBIp was internalized by caveolae-mediated endocytosis, and the internalized TGFBIp accumulated after treatment with bafilomycin A1, an inhibitor of lysosomal degradation. In addition, the proteasome inhibitor MG132 inhibits the endocytosis of TGFBIp. Co-immunoprecipitation revealed that TGFBIp interacted with integrin αVβ3. Moreover, treatment with arginine-glycine-aspartic acid (RGD) tripeptide suppressed the internalization of TGFBIp. These insights on TGFBIp trafficking could lead to the identification of novel targets and the development of new therapies for TGFBI-linked corneal dystrophy.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Amino Acid Motifs
  • Caveolae / metabolism*
  • Child
  • Corneal Diseases / pathology
  • Endocytosis*
  • Endoplasmic Reticulum / metabolism
  • Extracellular Matrix Proteins / chemistry
  • Extracellular Matrix Proteins / metabolism*
  • Female
  • Fibroblasts / cytology
  • Fibroblasts / pathology
  • Golgi Apparatus / metabolism
  • Humans
  • Integrin alphaVbeta3 / metabolism
  • Lysosomes / metabolism*
  • Male
  • Proteasome Endopeptidase Complex / metabolism
  • Proteolysis
  • Transforming Growth Factor beta / chemistry
  • Transforming Growth Factor beta / metabolism*
  • Ubiquitin / metabolism
  • Young Adult

Substances

  • Extracellular Matrix Proteins
  • Integrin alphaVbeta3
  • Transforming Growth Factor beta
  • Ubiquitin
  • betaIG-H3 protein
  • Proteasome Endopeptidase Complex

Grants and funding

This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (NRF 2013R1A1A2012958) and by the National Research Foundation of Korea (NRF) grant funded by the Korean government (MEST) (2011-0028699). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.