KCNIP1 (potassium channel-interacting protein 1) functions as a regulatory subunit of Kv4 voltage-gated potassium channels, particularly Kv4.1 and Kv4.2 1. It modulates channel density, inactivation kinetics, and recovery from inactivation in a calcium-dependent manner 1. Structurally, KCNIP1 captures both the N and C termini of Kv4.2 to prevent N-type inactivation and stabilize gating helices, thereby enabling rapidly activating and inactivating A-type currents that prevent backpropagation of action potentials 1. KCNIP1 is expressed differentially across brain regions and tissues, with alternatively spliced variants contributing to functional diversity 2. Clinically, KCNIP1 dysregulation associates with multiple conditions. A common copy number variant in KCNIP1's first intron strongly predicts atrial fibrillation risk 3, with overexpression inducing arrhythmias in zebrafish 3. KCNIP1 copy number gains associate with type 2 diabetes susceptibility, correlating with elevated fasting glucose and impaired insulin secretion 4, 5. KCNIP1 inhibition increases glucose-dependent insulin secretion 5. Additionally, KCNIP1 polymorphisms associate with attention-deficit/hyperactivity disorder risk 6, and DNA methylation changes at KCNIP1 correlate with depression severity 7.