Accessory protein that interacts with and modulates the function of G-protein coupled receptors including calcitonin gene-related peptide type 1 receptor (CALCRL), calcitonin receptor (CALCR) and G-protein coupled estrogen receptor 1 (GPER1). Required for the transport of CALCRL and GPER1 receptors to the plasma membrane. Plays a role in cardioprotection by reducing cardiac hypertrophy and perivascular fibrosis in a GPER1-dependent manner. Together with CALCRL, form a receptor complex for adrenomedullin/ADM and intermedin/ADM2. Together with CALCR, act as a receptor complex for amylin/IAPP