DLG1 functions upstream of SDCCAG3 and IFT20 to control ciliary targeting of polycystin-2
Csenge K. Rezi, Mariam G. Aslanyan, Gaurav D. Diwan, Tao Cheng, Mohamed Chamlali, Katrin Junger, Zeinab Anvarian, Esben Lorentzen, Kleo B. Pauly, Yasmin Afshar-Bahadori, Eduardo Felipe Alves Fernandes, Feng Qian, Sébastien Tosi, Søren T. Christensen, Stine F. Pedersen, Kristian Strømgaard, Robert B. Russell, Jeffrey H. Miner, Moe R. Mahjoub, Karsten Boldt, Ronald Roepman, Lotte B. Pedersen
Abstract
Polarized vesicular trafficking directs specific receptors and ion channels to cilia, but the underlying mechanisms are poorly understood. Here we describe a role for DLG1, a core component of the Scribble polarity complex, in regulating ciliary protein trafficking in kidney epithelial cells. Conditional knockout of Dlg1 in mouse kidney causes ciliary elongation and cystogenesis, and cell-based proximity labeling proteomics and fluorescence microscopy show alterations in the ciliary proteome upon loss of DLG1. Specifically, the retromer-associated protein SDCCAG3, IFT20, and polycystin-2 (PC2) are reduced in the cilia of DLG1-deficient cells compared to control cells. This phenotype is recapitulated in vivo and rescuable by re-expression of wild-type DLG1, but not a Congenital Anomalies of the Kidney and Urinary Tract (CAKUT)-associated DLG1 variant, p.T489R. Finally, biochemical approaches and Alpha Fold modelling suggest that SDCCAG3 and IFT20 form a complex that associates, at least indirectly, with DLG1. Our work identifies a key role for DLG1 in regulating ciliary protein composition and suggests that ciliary dysfunction of the p.T489R DLG1 variant may contribute to CAKUT.