Disrupted TSH Receptor Expression in Female Mouse Lung Fibroblasts Alters Subcellular IGF-1 Receptor Distribution

Endocrinology. 2015 Dec;156(12):4731-40. doi: 10.1210/en.2015-1464. Epub 2015 Sep 21.

Abstract

A relationship between the actions of TSH and IGF-1 was first recognized several decades ago. The close physical and functional associations between their respective receptors (TSHR and IGF-1R) has been described more recently in thyroid epithelium and human orbital fibroblasts as has the noncanonical behavior of IGF-1R. Here we report studies conducted in lung fibroblasts from female wild-type C57/B6 (TSHR(+/+)) mice and their littermates in which TSHR has been knocked out (TSHR(-/-)). Flow cytometric analysis revealed that cell surface IGF-1R levels are substantially lower in TSHR(-/-) fibroblasts compared with TSHR(+/+) fibroblasts. Confocal immunofluorescence microscopy revealed similar divergence with regard to both cytoplasmic and nuclear IGF-1R. Western blot analysis demonstrated both intact IGF-1R and receptor fragments in both cellular compartments. In contrast, IGF-1R mRNA levels were similar in fibroblasts from mice without and with intact TSHR expression. IGF-1 treatment of TSHR(+/+) fibroblasts resulted in reduced nuclear and cytoplasmic staining for IGF-1Rα, whereas it enhanced the nuclear signal in TSHR(-/-) cells. In contrast, IGF-1 enhanced cytoplasmic IGF-1Rβ in TSHR(-/-) fibroblasts while increasing the nuclear signal in TSHR(+/+) cells. These findings indicate the intimate relationship between TSHR and IGF-1R found earlier in human orbital fibroblasts also exists in mouse lung fibroblasts. Furthermore, the presence of TSHR in these fibroblasts influenced not only the levels of IGF-1R protein but also its subcellular distribution and response to IGF-1. They suggest that the mouse might serve as a suitable model for delineating the molecular mechanisms overarching these two receptors.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Blotting, Western
  • Cell Membrane / metabolism
  • Cell Nucleus / metabolism
  • Cytoplasm / metabolism
  • Female
  • Fibroblasts / metabolism*
  • Flow Cytometry
  • Lung / cytology
  • Mice
  • Mice, Knockout
  • Microscopy, Confocal
  • Microscopy, Fluorescence
  • RNA, Messenger / metabolism*
  • Receptor, IGF Type 1 / genetics*
  • Receptor, IGF Type 1 / metabolism
  • Receptors, Thyrotropin / genetics*
  • Reverse Transcriptase Polymerase Chain Reaction

Substances

  • RNA, Messenger
  • Receptors, Thyrotropin
  • Receptor, IGF Type 1