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The Sema domain, a protein interacting module, of semaphorin 4B (Sema4B) Sema4B, expressed in T and B cells, is an immune semaphorin. It functions as a negative regulatory of basophils through T cell-basophil contacts and it significantly inhibits IL-4 and IL-6 production from basophils in response to various stimuli, including IL-3 and papain. In addition, T cell-derived Sema4B suppresses basophil-mediated Th2 skewing and humoral memory responses. Sema4B may be also involved in lung cancer cell mobility by inducing the degradation of CLCP1 (CUB, LCCL-homology, coagulation factor V/VIII homology domains protein). Sema4B is characterized by a PDZ-binding motif at the carboxy-terminus, which mediates interaction with the post-synaptic density protein PSD-95/SAP90, which is thought to play a central role during synaptogenesis and in the structure and function of post-synaptic specializations of excitatory synapses. Sema4B belongs to class 4 transmembrane semaphorin family proteins. 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. |
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