Epac (Exchange Protein Directly Activated by cAMP) is a class of guanine nucleotide exchange factors (GEFs) that respond to cAMP signaling, including two family members, Epac1 and Epac2. Epac proteins have a cAMP-binding domain and a guanine nucleotide exchange factor (GEF) domain, primarily located in the cytoplasm and cell membrane. Epac activates Rap small G proteins by binding to cAMP, participating in the regulation of various biological processes such as cell adhesion, secretion, and gene expression. Epac is expressed in various cells and tissues, with its expression and activity regulated by cAMP levels. Tissue-specific expression and mutations of Epac genes are associated with various diseases, including cardiovascular diseases, diabetes, and neurological disorders.