Complement membrane attack complexes activate noncanonical NF-κB by forming an Akt+ NIK+ signalosome on Rab5+ endosomes

Proc Natl Acad Sci U S A. 2015 Aug 4;112(31):9686-91. doi: 10.1073/pnas.1503535112. Epub 2015 Jul 20.

Abstract

Complement membrane attack complexes (MACs) promote inflammatory functions in endothelial cells (ECs) by stabilizing NF-κB-inducing kinase (NIK) and activating noncanonical NF-κB signaling. Here we report a novel endosome-based signaling complex induced by MACs to stabilize NIK. We found that, in contrast to cytokine-mediated activation, NIK stabilization by MACs did not involve cIAP2 or TRAF3. Informed by a genome-wide siRNA screen, instead this response required internalization of MACs in a clathrin-, AP2-, and dynamin-dependent manner into Rab5(+)endosomes, which recruited activated Akt, stabilized NIK, and led to phosphorylation of IκB kinase (IKK)-α. Active Rab5 was required for recruitment of activated Akt to MAC(+) endosomes, but not for MAC internalization or for Akt activation. Consistent with these in vitro observations, MAC internalization occurred in human coronary ECs in vivo and was similarly required for NIK stabilization and EC activation. We conclude that MACs activate noncanonical NF-κB by forming a novel Akt(+)NIK(+) signalosome on Rab5(+) endosomes.

Keywords: complement; endothelial cell; inflammation; membrane attack complex; signaling.

Publication types

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

MeSH terms

  • Animals
  • Baculoviral IAP Repeat-Containing 3 Protein
  • Clathrin / metabolism
  • Complement Membrane Attack Complex / metabolism*
  • Coronary Vessels / drug effects
  • Coronary Vessels / metabolism
  • Endocytosis / drug effects
  • Endosomes / drug effects
  • Endosomes / metabolism*
  • Enzyme Stability / drug effects
  • Flow Cytometry
  • Human Umbilical Vein Endothelial Cells / drug effects
  • Human Umbilical Vein Endothelial Cells / metabolism
  • Humans
  • Hydrazones / pharmacology
  • Inhibitor of Apoptosis Proteins / metabolism
  • Mice, SCID
  • NF-kappa B / metabolism*
  • NF-kappaB-Inducing Kinase
  • Protein Biosynthesis / drug effects
  • Protein Serine-Threonine Kinases / metabolism*
  • Proto-Oncogene Proteins c-akt / metabolism*
  • RNA, Small Interfering / metabolism
  • Secretory Vesicles / drug effects
  • Secretory Vesicles / metabolism
  • Signal Transduction* / drug effects
  • TNF Receptor-Associated Factor 3 / metabolism
  • Ubiquitin-Protein Ligases / metabolism
  • rab5 GTP-Binding Proteins / metabolism*

Substances

  • Clathrin
  • Complement Membrane Attack Complex
  • Hydrazones
  • Inhibitor of Apoptosis Proteins
  • N'-(3,4-dihydroxybenzylidene)-3-hydroxy-2-naphthahydrazide
  • NF-kappa B
  • RNA, Small Interfering
  • TNF Receptor-Associated Factor 3
  • BIRC3 protein, human
  • Baculoviral IAP Repeat-Containing 3 Protein
  • Ubiquitin-Protein Ligases
  • Protein Serine-Threonine Kinases
  • Proto-Oncogene Proteins c-akt
  • rab5 GTP-Binding Proteins