NALF1 (encoded by FAM155A) is an auxiliary subunit of the NALCN sodium leak channel complex, which regulates neuronal resting membrane potential and excitability 1. As a structural component, FAM155A forms extensive interactions with NALCN's extracellular loops and creates an extracellular dome that stabilizes the channel in the membrane and shields the ion-selectivity filter 23. The NALCN channelosome, comprising NALCN, FAM155A, UNC79, and UNC80, maintains a tightly closed pore gate with low open probability under basal conditions 1. NALCN-mediated sodium currents control neuronal excitability linked to respiration, locomotion, and circadian rhythm 2. Mutations in NALCN and its auxiliary subunits cause severe developmental and neurological disorders 1, while FAM155A variants associate with diverticulitis susceptibility, though the mechanistic link remains unclear 45. Additionally, FAM155A promoter hypermethylation in clear cell renal carcinoma correlates with aggressive tumor phenotype and early metastasis 6. The structural architecture of the NALCN channelosome provides a framework for understanding disease mechanisms and developing targeted therapeutics for channelopathies.