Integrin alpha 1, also known as VLA-1, CD49a, and Laminin and Collagen Receptor, is expressed on smooth muscle cells, osteoblasts, adipocytes, and intestinal epithelium. It forms a noncovalent heterodimer with Integrin beta 1 and serves as a divalent-cation dependent receptor for Collagen types I, IV, VI, XIII, and XVI. It also binds the diarrhea-associated NSP4 enterotoxin of rotavirus.