The Role of Semaphorins and Their Receptors in Gliomas

Figure 1

Semaphorins and their receptors. Schematic diagram to illustrate the structural features of different classes of semaphorins, plexins and neuropilins. Members of class 2 and 3 semaphorins are secreted, whereas semaphorins 1, 4–6 are single-pass transmembrane proteins. Class 7 semaphorin is membrane-bound via a GPI-anchor. All known semaphorins and plexins are characterized by the presence of a sema domain at the amino-terminus. While semaphorins are structurally diverse, plexin members are well-conserved and feature PSI and IPT domains in the extracellular moiety, and a split intracellular GTPase activating protein (GAP) domain. Plexin-Bs are distinctive by the presence of a PDZ domain binding site at the C-terminus. Neuropilins are transmembrane receptors that feature two complement binding (CUB) domains and FV/FVIII coagulating factor-like domain, and a MAM domain in the extracellular portion. Ig, immunoglobulin-like; TM, transmembrane domain; CD, cytoplasmic domain.