Ubiquitylation of the ER-Shaping Protein Lunapark via the CRL3KLHL12 Ubiquitin Ligase Complex

• Main Authors: Laurensia Yuniati, Angela Lauriola, Manouk Gerritsen, Susana Abreu, Eric Ni, Chiara Tesoriero, Jacob O. Onireti, Teck Yew Low, Albert J.R. Heck, Andrea Vettori, Timothy Cardozo, Daniele Guardavaccaro
• Format: Article
• Language: English
• Published: Elsevier 2020-05-01
• Series: Cell Reports
• Subjects: cullin-RING ligases; ubiquitin; endoplasmic reticulum; ER three-way junction; Lunapark; mTORC1
• Online Access: http://www.sciencedirect.com/science/article/pii/S2211124720306173

Summary: Cullin-RING ligases (CRLs) control key cellular processes by promoting ubiquitylation of a multitude of soluble cytosolic and nuclear proteins. Subsets of CRL complexes are recruited and activated locally at cellular membranes; however, few CRL functions and substrates at these distinct cellular compartments are known. Here, we use a proteomic screen to identify proteins that are ubiquitylated at cellular membranes and found that Lunapark, an endoplasmic reticulum (ER)-shaping protein localized to ER three-way junctions, is ubiquitylated by the CRL3KLHL12 ubiquitin ligase. We demonstrate that Lunapark interacts with mechanistic target of rapamycin complex-1 (mTORC1), a central cellular regulator that coordinates growth and metabolism with environmental conditions. We show that mTORC1 binds Lunapark specifically at three-way junctions, and lysosomes, where mTORC1 is activated, make contact with three-way junctions where Lunapark resides. Inhibition of Lunapark ubiquitylation results in neurodevelopmental defects indicating that KLHL12-dependent ubiquitylation of Lunapark is required for normal growth and development.