Planar Cell Polarity Effector Proteins Inturned and Fuzzy Form a Rab23 GEF Complex

Andreas Gerondopoulos, Helen Strutt, Nicola L. Stevenson, Tomoaki Sobajima, Tim P. Levine, David J. Stephens, David Strutt, Francis A. Barr*

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

17 Citations (Scopus)
135 Downloads (Pure)


A subset of Rab GTPases have been implicated in cilium formation in cultured mammalian cells [1–6]. Rab11 and Rab8, together with their GDP-GTP exchange factors (GEFs), TRAPP-II and Rabin8, promote recruitment of the ciliary vesicle to the mother centriole and its subsequent maturation, docking, and fusion with the cell surface [2–5]. Rab23 has been linked to cilium formation and membrane trafficking at mature cilia [1, 7, 8]; however, the identity of the GEF pathway activating Rab23, a member of the Rab7 subfamily of Rabs, remains unclear. Longin-domain-containing complexes have been shown to act as GEFs for Rab7 subfamily GTPases [9–12]. Here, we show that Inturned and Fuzzy, proteins previously implicated as planar cell polarity (PCP) effectors and in developmentally regulated cilium formation [13, 14], contain multiple longin domains characteristic of the Mon1-Ccz1 family of Rab7 GEFs and form a specific Rab23 GEF complex. In flies, loss of Rab23 function gave rise to defects in planar-polarized trichome formation consistent with this biochemical relationship. In cultured human and mouse cells, Inturned and Fuzzy localized to the basal body and proximal region of cilia, and cilium formation was compromised by depletion of either Inturned or Fuzzy. Cilium formation arrested after docking of the ciliary vesicle to the mother centriole but prior to axoneme elongation and fusion of the ciliary vesicle and plasma membrane. These findings extend the family of longin domain GEFs and define a molecular activity linking Rab23-regulated membrane traffic to cilia and planar cell polarity.

Original languageEnglish
Pages (from-to)3323 - 3330.e8
Number of pages17
JournalCurrent Biology
Issue number19
Early online date26 Sep 2019
Publication statusPublished - 7 Oct 2019


  • cilia
  • primary cilium
  • planar polarity
  • Rab23
  • guanine
  • nucleotide exchange factor
  • longin domain
  • C-plane
  • Inturned
  • Fuzzy
  • Carpenter syndrome


Dive into the research topics of 'Planar Cell Polarity Effector Proteins Inturned and Fuzzy Form a Rab23 GEF Complex'. Together they form a unique fingerprint.

Cite this