MOCA (modifier of cell adhesion), also known as Presenilin-binding protein (PBP) or dedicator of cytokinesis protein 3 (DOCK3), is a 2030 amino acid cytoplasmic protein belonging to the DOCK family. MOCA interacts with Presenilin proteins and has the ability to stimulate Tau phosphorylation suggesting that MOCA may be involved in Alzheimer disease. MOCA is also thought to be a guanine nucleotide exchange factor (GEF) which activates small GTPases by exchanging bound GDP for free GTP. Analysis of ectopic expression suggests that MOCA may affect the function of small GTPases involved in the regulation of Actin cytoskeleton or cell adhesion receptors. MOCA is localized to the neuropil, and sometimes in pyramidal cells, in normal brains, while in Alzheimer disease brains, MOCA is present in neurofibrillary tangles.