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The Sema domain, a protein interacting module, of class 4 semaphorins (Sema4) Class 4 semaphorins (Sema4s) are transmembrane regulator molecules involved in the development of the nervous system, immune response, cytoskeletal organization, angiogenesis, and cell-cell interactions. There are 7 distinct subfamilies in class 4 semaphorins, named 4A to 4G. Several class 4 subfamilies play important roles in the immune system and are called "immune semaphorins". Sema4A plays critical roles in T cell-DC interactions in the immune response. Sema4D/CD100, expressed by lymphocytes, promotes the aggregation and survival of B lymphocytes and inhibits cytokine-induced migration of immune cells in vitro. It is required for normal activation of B and T lymphocytes. Sema4B negatively regulates basophil functions through T cell-basophil contacts and significantly inhibits IL-4 and IL-6 production from basophils in response to various stimuli, including IL-3 and papain. Sema4s not only influence the activation state of cells but also modulate their migration and survival. The effects of Sema4s on nonlymphoid cells are mediated by plexin D1 and plexin Bs. The Sema4G and Sema4C genes are expressed in the developing cerebellar cortex and are involved in neural tube closure and development of cerebellar granules cells through receptor plexin B2. 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. |
Jiyao W et al.(2023). "The conserved domain database in 2023.",