PGRMC2 Is an Intracellular Haem Chaperone Critical for Adipocyte Function

Nature. 2019 Dec;576(7785):138-142. doi: 10.1038/s41586-019-1774-2. Epub 2019 Nov 20.

Abstract

Haem is an essential prosthetic group of numerous proteins and a central signalling molecule in many physiologic processes1,2. The chemical reactivity of haem means that a network of intracellular chaperone proteins is required to avert the cytotoxic effects of free haem, but the constituents of such trafficking pathways are unknown3,4. Haem synthesis is completed in mitochondria, with ferrochelatase adding iron to protoporphyrin IX. How this vital but highly reactive metabolite is delivered from mitochondria to haemoproteins throughout the cell remains poorly defined3,4. Here we show that progesterone receptor membrane component 2 (PGRMC2) is required for delivery of labile, or signalling haem, to the nucleus. Deletion of PGMRC2 in brown fat, which has a high demand for haem, reduced labile haem in the nucleus and increased stability of the haem-responsive transcriptional repressors Rev-Erbα and BACH1. Ensuing alterations in gene expression caused severe mitochondrial defects that rendered adipose-specific PGRMC2-null mice unable to activate adaptive thermogenesis and prone to greater metabolic deterioration when fed a high-fat diet. By contrast, obese-diabetic mice treated with a small-molecule PGRMC2 activator showed substantial improvement of diabetic features. These studies uncover a role for PGRMC2 in intracellular haem transport, reveal the influence of adipose tissue haem dynamics on physiology and suggest that modulation of PGRMC2 may revert obesity-linked defects in adipocytes.

Publication types

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

MeSH terms

  • Adipocytes / metabolism*
  • Animals
  • Heme / metabolism*
  • Homeostasis
  • Humans
  • Intracellular Space / metabolism
  • Male
  • Membrane Proteins / deficiency
  • Membrane Proteins / genetics
  • Membrane Proteins / metabolism*
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Mitochondria / metabolism
  • Molecular Chaperones / metabolism
  • Receptors, Progesterone / deficiency
  • Receptors, Progesterone / genetics
  • Receptors, Progesterone / metabolism*
  • Transcription, Genetic

Substances

  • Membrane Proteins
  • Molecular Chaperones
  • PGRMC2 protein, human
  • PGRMC2 protein, mouse
  • Receptors, Progesterone
  • Heme