Required for calcium-mediated regulation of ciliary beat frequency and mucociliary clearance in the airway. Might be involved in the regulation of intracellular calcium in tracheal epithelial cells. Interacts with LYPD3 and DAG1 (alphaDAG1). Expressed in the ciliated cells of the airway epithelium. Not detected in the mucous cells. Knockout mice develop ciliated cells with normal-appearing cilia and histology. However, ciliary beat frequency was lower in airways from knockout mice compared with control mice in presence of calcium (20% lower in the absence of stimulation, 35% lower after ATP stimulation). Knockout mice show reduced mucociliary clearance. Knockout mice do not seem to show endoplasmic reticulum stress response. Belongs to the AGR family.