DNAJC16 (also known as ERdj8) is an endoplasmic reticulum (ER) membrane protein that plays a critical role in regulating autophagosome size during their formation. The protein localizes to a specialized ER subdomain enriched with phosphatidylinositol synthase (PIS) and autophagy-related proteins 1. DNAJC16 contains both DnaJ and thioredoxin (TRX) domains that are essential for its function 2. Mechanistically, DNAJC16 overexpression extends autophagosome size, enabling engulfment of larger substrates, while its depletion impairs the capacity to engulf large targets such as somatic mitochondria 2. Beyond autophagy, DNAJC16 has emerged as a tumor suppressor in lung adenocarcinoma, where its circular RNA form (circDNAJC16) is downregulated in advanced stages and predicts poor survival 3. CircDNAJC16 suppresses tumor progression by sequestering the oncogenic miRNA miR-93-5p, thereby activating CDKN1A/p21-mediated cell cycle arrest and inhibiting epithelial-mesenchymal transition 3. Additionally, genetic variants in DNAJC16 (rs7546668) are significantly associated with gout susceptibility in genome-wide association studies 4. DNAJC16 represents both a fundamental regulator of cellular autophagy and a potential therapeutic target for cancer and metabolic diseases.