ACBD4 (acyl-CoA binding domain containing 4) is a peroxisomal tail-anchored membrane protein that binds medium- and long-chain acyl-CoA esters and functions as an intracellular carrier of these lipid molecules 1. Primary to its function, ACBD4 interacts with the endoplasmic reticulum (ER) protein VAPB via its FFAT motif to promote peroxisome-ER membrane contact sites 12, though this tethering function appears distinct from ACBD5. Unlike ACBD5, loss of ACBD4 does not reduce peroxisome-ER connections or cause very-long-chain fatty acid (VLCFA) accumulation; instead, ACBD4 loss increases the rate of VLCFA β-oxidation, suggesting regulatory rather than primary tethering roles 3. ACBD4 expression is modulated in lipid metabolism contexts, including upregulation in fatty liver development 4. Genetically, ACBD4 is a pleiotropic locus influencing hippocampal volumes and correlates with neuropsychiatric traits including Parkinson's disease risk 5. ACBD4 is also a novel p53-responsive gene activated during p53-dependent stress responses 6. These findings establish ACBD4 as a multifunctional regulator at the peroxisome-ER interface with roles in cellular lipid metabolism and neuropsychiatric disease susceptibility.