Model of ACBD5–VAPB interaction and regulation at the peroxisome–ER interface . Peroxisomal ACBD5 and ER-resident VAPB interact via the FFAT and MSP domains to enable peroxisome–ER contacts. The FFAT-MSP interaction involves the FFAT core (VYCDSME) and flanking acidic tract. ACBD5 phosphorylation (P) can promote (green, acidic tract) or inhibit (red, FFAT core) VAPB interaction. GSK3β regulates the ACBD5–VAPB interaction via phosphorylation of the serine in the FFAT core. ACB, acyl-CoA binding domain.