ACAP2 (ArfGAP with coiled-coil, ankyrin repeat and PH domains 2) is a GTPase-activating protein (GAP) that primarily functions as a negative regulator of ARF6 activity 1. It contains multiple structural domains including coiled-coil, pleckstrin homology, Arf GAP domains, and three ankyrin-repeat regions 1. ACAP2 is recruited to peripheral tubular membranes and inhibits ARF6-dependent membrane ruffles and protrusions, functioning in endosomal recycling and actin cytoskeleton organization 1. In oligodendrocyte differentiation, the Rab35/ACAP2 complex negatively regulates morphological differentiation by suppressing ARF6 activity; knockdown of ACAP2 promotes differentiation and myelination 2. ACAP2 also functions as a pro-apoptotic factor through phosphoinositide-binding activity that inactivates AKT survival signaling 3. Notably, while full-length ACAP2 protein has roles in normal physiology, circular RNA ACAP2 (circRNA ACAP2) is dysregulated in disease contexts. CircRNA ACAP2 is upregulated in myocardial infarction, where it promotes cardiomyocyte apoptosis by enhancing miR-532 maturation or sponging miR-29 [PMID:34139744; 43]. In colorectal cancer, circRNA ACAP2 promotes tumor progression and radioresistance through the miR-143-3p/FZD4 axis, activating Wnt/β-catenin signaling 5.