May be involved in retrograde transport from endosomes to the trans-Golgi network (TGN). TMEM87B mutations may be involved in restrictive cardiomyopathy (RCM), a rare non-ischemic myocardial disease. RCM is characterized by restrictive ventricular-filling physiology in the presence of normal or reduced diastolic and/or systolic volumes (of 1 or both ventricles), biatrial enlargement, and normal ventricular wall thickness. Belongs to the LU7TM family. TMEM87 subfamily.