Figure 3.

Soluble cytosolic reticulophagy receptors. CALCOCO1 is recruited to the cytosolic face of the ER by binding VAPA/B through its C-terminal FFAT-like domain. CALCOCO1 binds GABARAP via multivalent interactions; its amino-terminal CLIR interacts with the GABARAP LIR-docking site (LDS) and its carboxy-terminal UIR interacts with the GABARAP ubiquitin interacting motif docking site (UDS). CDK5RAP3 is a core component of the UFMylation machinery that directs ribosomal protein UFMylation during stalling at the ER translocon; following ribosomal protein UFMylation, CDK5RAP3-DDRGK1/UFBP1 complexes can be released from this role, and bind GABARAP via a sAIM motif in CDK5RAP3, thereby promoting phagophore recruitment for reticulophagy. SRP, signal recognition particle; SRPR, signal recognition particle receptor.