Ablation of SUN2-containing LINC complexes drives cardiac hypertrophy without interstitial fibrosis

Mol Biol Cell. 2019 Jul 1;30(14):1664-1675. doi: 10.1091/mbc.E18-07-0438. Epub 2019 May 15.

Abstract

The cardiomyocyte cytoskeleton, including the sarcomeric contractile apparatus, forms a cohesive network with cellular adhesions at the plasma membrane and nuclear--cytoskeletal linkages (LINC complexes) at the nuclear envelope. Human cardiomyopathies are genetically linked to the LINC complex and A-type lamins, but a full understanding of disease etiology in these patients is lacking. Here we show that SUN2-null mice display cardiac hypertrophy coincident with enhanced AKT/MAPK signaling, as has been described previously for mice lacking A-type lamins. Surprisingly, in contrast to lamin A/C-null mice, SUN2-null mice fail to show coincident fibrosis or upregulation of pathological hypertrophy markers. Thus, cardiac hypertrophy is uncoupled from profibrotic signaling in this mouse model, which we tie to a requirement for the LINC complex in productive TGFβ signaling. In the absence of SUN2, we detect elevated levels of the integral inner nuclear membrane protein MAN1, an established negative regulator of TGFβ signaling, at the nuclear envelope. We suggest that A-type lamins and SUN2 play antagonistic roles in the modulation of profibrotic signaling through opposite effects on MAN1 levels at the nuclear lamina, suggesting a new perspective on disease etiology.

Publication types

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

MeSH terms

  • Animals
  • Cardiomegaly / metabolism*
  • Cardiomegaly / pathology*
  • Cell Adhesion
  • Cell Nucleus Shape
  • DNA-Binding Proteins / metabolism
  • Fibrosis
  • Gene Deletion*
  • Integrins / metabolism
  • MAP Kinase Signaling System
  • Membrane Proteins / deficiency
  • Membrane Proteins / metabolism*
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Multiprotein Complexes / metabolism*
  • Myocardium / metabolism
  • Myocardium / pathology
  • Myocardium / ultrastructure
  • Nuclear Envelope / metabolism
  • Proto-Oncogene Proteins c-akt / metabolism
  • Sarcomeres / metabolism
  • Sarcomeres / ultrastructure
  • Telomere-Binding Proteins / deficiency
  • Telomere-Binding Proteins / metabolism*
  • Transforming Growth Factor beta / metabolism

Substances

  • DNA-Binding Proteins
  • Integrins
  • Man1 protein, mouse
  • Membrane Proteins
  • Multiprotein Complexes
  • Sun2 protein, mouse
  • Telomere-Binding Proteins
  • Transforming Growth Factor beta
  • Proto-Oncogene Proteins c-akt