Recently, a novel plaque-associated protein, collagenous Alzheimer amy-loid plaque component (CLAC), was identified in brains from patients with Alzheimer’s disease. CLAC is derived from a type II transmembrane colla-gen precursor protein, termed CLAC-P (collagen XXV). The biological function and the contribution of CLAC to the pathogenesis of Alzheimer’s disease and plaque formation are unknown.