Stromal membrane associated protein-1 (SMAP1, also known as small ArfGAP1) is a GTPase activating protein that plays a role in clathrin-dependent endocytosis. It may also play a role in erythropoiesis. SMAP1 is known to interact with ARF6 and the clathrin heavy chains via the clathrin box-like motif. SMAP1 is expressed in bone marrow, adrenal gland, trachea, lymph node, spinal cord, peripheral blood leukocytes, thyroid and stomach.