Wnt family member 4 (WNT4) and WNT3A activate cell-autonomous Wnt signaling independent of porcupine O- acyltransferase or Wnt secretion

J Biol Chem. 2019 Dec 27;294(52):19950-19966. doi: 10.1074/jbc.RA119.009615. Epub 2019 Nov 18.

Abstract

Porcupine O-acyltransferase (PORCN) is considered essential for Wnt secretion and signaling. However, we observed that PORCN inhibition does not phenocopy the effects of WNT4 knockdown in WNT4-dependent breast cancer cells. This suggests a unique relationship between PORCN and WNT4 signaling. To examine the role of PORCN in WNT4 signaling, here we overexpressed WNT4 or WNT3A in breast cancer, ovarian cancer, and fibrosarcoma cell lines. Conditioned media from these lines and co-culture systems were used to assess the dependence of Wnt secretion and activity on the critical Wnt secretion proteins PORCN and Wnt ligand secretion (WLS) mediator. We observed that WLS is universally required for Wnt secretion and paracrine signaling. In contrast, the dependence of WNT3A secretion and activity on PORCN varied across the cell lines, and WNT4 secretion was PORCN-independent in all models. Surprisingly, WNT4 did not exhibit paracrine activity in any tested context. Absent the expected paracrine activity of secreted WNT4, we identified cell-autonomous Wnt signaling activation by WNT4 and WNT3A, independent of PORCN or Wnt secretion. The PORCN-independent, cell-autonomous Wnt signaling demonstrated here may be critical in WNT4-driven cellular contexts or in those that are considered to have dysfunctional Wnt signaling.

Keywords: PORCN; WNT3A; WNT4; Wnt pathway; Wnt signaling; breast cancer; cancer biology; cell growth; cell signaling; glycoprotein secretion; ovarian cancer; protein secretion.

Publication types

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

MeSH terms

  • Acyltransferases / antagonists & inhibitors
  • Acyltransferases / genetics
  • Acyltransferases / metabolism*
  • Cell Line, Tumor
  • Cell Proliferation
  • Coculture Techniques
  • Culture Media, Conditioned / chemistry
  • Fulvestrant / pharmacology
  • Humans
  • Intracellular Signaling Peptides and Proteins / antagonists & inhibitors
  • Intracellular Signaling Peptides and Proteins / genetics
  • Intracellular Signaling Peptides and Proteins / metabolism
  • Membrane Proteins / antagonists & inhibitors
  • Membrane Proteins / genetics
  • Membrane Proteins / metabolism*
  • Paracrine Communication
  • Protein Transport
  • RNA Interference
  • RNA, Small Interfering / metabolism
  • Receptors, G-Protein-Coupled / antagonists & inhibitors
  • Receptors, G-Protein-Coupled / genetics
  • Receptors, G-Protein-Coupled / metabolism
  • Wnt Signaling Pathway* / drug effects
  • Wnt3A Protein / antagonists & inhibitors
  • Wnt3A Protein / genetics
  • Wnt3A Protein / metabolism*
  • Wnt4 Protein / antagonists & inhibitors
  • Wnt4 Protein / genetics
  • Wnt4 Protein / metabolism*

Substances

  • Culture Media, Conditioned
  • Intracellular Signaling Peptides and Proteins
  • Membrane Proteins
  • RNA, Small Interfering
  • Receptors, G-Protein-Coupled
  • WLS protein, human
  • Wnt3A Protein
  • Wnt4 Protein
  • Fulvestrant
  • Acyltransferases
  • PORCN protein, human