Endoplasmic reticulum (ER)-anchored autophagy regulator which exists in an inactive state under basal conditions but is activated following cellular stress (PubMed:34338405). When activated, induces ER fragmentation and mediates ER delivery into lysosomes through sequestration into autophagosomes via interaction with ATG8 family proteins (PubMed:34338405). Promotes ER membrane curvature and ER tubulation required for subsequent ER fragmentation and engulfment into autophagosomes (PubMed:33826365). Required for collagen quality control in a LIR motif-dependent manner (By similarity). Mediates NRF1-enhanced neurite outgrowth (PubMed:26040720). {ECO:0000250|UniProtKB:Q9CQV4, ECO:0000269|PubMed:26040720, ECO:0000269|PubMed:33826365, ECO:0000269|PubMed:34338405}. This is the function of RETREG3 (reticulophagy regulator family member 3, ENSG00000141699).