Glycoprotein which is a component of the gelatinous extracellular matrix in the cupulae of the vestibular organ. Detected in the acellular cupulae of the vestibular organ, and also in support cells adjacent to the cupula (at protein level). Proteolytically cleaved before the transmembrane segment to yield the secreted form found in the extracellular matrix of the cupula. N-glycosylated.