In mice, Sema5A has been identified as a protein that induces inhibitory responses during optic nerve development []. It also has been identified as a candidate gene for causing idiopathic autism in humans []. Plexin B3 functions as a binding partner and receptor for Sema5A []. Sema5A is highly expressed in human pancreatic cancer cells and is associated with tumor growth, invasion and metastasis []. Sema5A belongs to class 5 semaphorin family of proteins, which are transmembrane glycoproteins characterised by unique thrombospondin specific repeats in the extracellular region of the protein []. Semaphorins are regulatory molecules in the development of the nervous system and in axonal guidance. They also play important roles in other biological processes, such as angiogenesis, immune regulation, respiration systems and cancer. The Sema domain is located at the N terminus and contains four disulfide bonds formed by eight conserved cysteine residues. It serves as a receptor-recognition and -binding module [].
