Substrate adapter for ufmylation, the covalent attachment of the ubiquitin-like modifier UFM1 to substrate proteins, which plays a key role in reticulophagy (also called ER-phagy) (PubMed:32160526). In response to endoplasmic reticulum stress, promotes recruitment of the E3 UFM1-protein ligase UFL1 to the endoplasmic reticulum membrane: in turn, UFL1 mediates ufmylation of proteins such as RPN1 and RPL26/uL24, promoting reticulophagy of endoplasmic reticulum sheets (PubMed:32160526). Ufmylation-dependent reticulophagy inhibits the unfolded protein response (UPR) by regulating ERN1/IRE1-alpha stability (PubMed:28128204, PubMed:32160526). Ufmylation in response to endoplasmic reticulum stress is essential for processes such as hematopoiesis or inflammatory response (By similarity). Required for TRIP4 ufmylation, thereby regulating nuclear receptors-mediated. transcription (PubMed:25219498). May play a role in NF-kappa-B-mediated transcription through regulation of the phosphorylation and the degradation of NFKBIA, the inhibitor of NF-kappa-B (PubMed:23675531). Plays a role in cartilage development through SOX9, inhibiting the ubiquitin-mediated proteasomal degradation of this transcriptional regulator (PubMed:28263186). Interacts with TRIP4; the interaction with TRIP4 is direct (PubMed:25219498). Interacts (via PCI domain) with UFL1 (PubMed:25219498, PubMed:32160526). Interacts with (unphosphorylated) ERN1/IRE1-alpha; interaction is dependent on UFM1 and takes place in response to endoplasmic reticulum stress, regulating ERN1/IRE1-alpha stability (PubMed:28128204). Interacts with NFKBIA (PubMed:23675531). Interacts with CDK5RAP3 (PubMed:20228063). Interacts with SOX9 (PubMed:28263186). Localizes to the endoplasmic reticulum membrane in response to endoplasmic reticulum stress. Widely expressed (at protein level). In the brain, highest levels in medulla oblongata, followed by cerebral cortex, cerebellum and frontal lobe. Ubiquitinated. Ubiquitination probably triggers proteasomal degradation and is negatively regulated by UFL1, the enzyme involved in the ufmylation of DDRGK1. Ufmylated; conjugated to ubiquitin-like protein UFM1, probably at Lys-267 by UFL1 (PubMed:20018847, PubMed:28128204). The relevance of ufmylation is however unclear: as DDRGK1 acts as substrate adapters for ufmylation, it is uncertain whether ufmylation is a collatoral effect of ufmylation process or is required to regulate its activity (PubMed:32160526). The disease is caused by variants affecting the gene represented in this entry. Belongs to the DDRGK1 family.