Structure of the ciliogenesis-associated CPLANE complex

Abstract

Dysfunctional cilia cause pleiotropic human diseases termed ciliopathies. These hereditary maladies are often caused by defects in cilia assembly, a complex event that is regulated by the ciliogenesis and planar polarity effector (CPLANE) proteins Wdpcp, Inturned, and Fuzzy. CPLANE proteins are essential for building the cilium and are mutated in multiple ciliopathies, yet their structure and molecular functions remain elusive. Here, we show that mammalian CPLANE proteins comprise a bona fide complex and report the near-atomic resolution structures of the human Wdpcp-Inturned-Fuzzy complex and of the mouse Wdpcp-Inturned-Fuzzy complex bound to the small guanosine triphosphatase Rsg1. Notably, the crescent-shaped CPLANE complex binds phospholipids such as phosphatidylinositol 3-phosphate via multiple modules and a CPLANE ciliopathy mutant exhibits aberrant lipid binding. Our study provides critical structural and functional insights into an enigmatic ciliogenesis-associated complex as well as unexpected molecular rationales for ciliopathies.

CPLANE Complex and Ciliopathies

“…A recent study carried out on mice and human cell lines has revealed that the complex adopts a crescent-like architecture, such that Wdpcp and Rsg1 are located at the ends of the crescent and bind to the central Intu-Fuz heterodimer on opposite sides. This creates a linear-type subunit interaction scheme that can be represented as Wdpcp-Intu-Fuz-Rsg1 [ 28 ].…”

“…Regarding the structure of the different proteins that conform the complex, Wdpcp (85.084 kDa) folds into a seven-bladed β-propeller belonging to the WD40 family, followed by an array of α helices [ 28 ]. Both Intu and Fuz have three longin-like domains (LD).…”

“…LD1 of Intu (105.648 kDa) and Fuz (45.679 kDa) adopts a canonical longin fold, LD2 adopts a longin-like fold and LD3 adopts a lamp longin-like fold [ 29 ]. The core structure of Rsg1 (28.534 kDa) follows the typical small GTPase fold characterised by a central six-stranded concave β sheet surrounded by five α helices [ 28 ]. Wdpcp mainly contacts Intu with a large interface area of 2609 Å 2 .…”

“…Intu contacts Fuz with a large buried surface area of 1898 Å 2 . Intu-Fuz heterodimer formation is mediated by LD1 and LD3 [ 28 ].…”

“…Nevertheless, it has been shown that Rsg1 interacts only with Fuz [ 28 ], and there is no interaction with the other elements of the complex as suspected [ 19 , 24 ]. The Fuz-Rsg1 interface spans an area of 1099 Å 2 and consists of Fuz LD1 and LD2 engaging the central β sheet of Rsg1 [ 28 ].…”