PLXNA4A

Plexin-A4 is a protein that in humans is encoded by the PLXNA4 gene.

Function

Plexin A4 binds to neuropilin 1 (Nrp1) and neuropilin 2 (Nrp2) and transduces signals from Sema3A, Sema6A, and Sema6B. These Nrp-plexin and semaphorin complexes initiate cascades that regulate diverse processes such as axon pruning and repulsion, dendritic attraction and branching, regulation of cell migration, vascular remodeling, and growth cone collapse. Both upregulation and downregulation of Plexin A4 has been observed following neural injury suggesting a dynamic role for Sema3A and Plexin A4 in neural maintenance and regeneration. Additionally, Sema3A and therefore its receptor, Plexin A4, have been implicated as possible components of fast-fatigable muscle fiber denervation in ALS.

Structure

Plexin A4 has ~1890 amino acids that include a likely signal sequence, transmembrane domain, and 12 extracellular N-linked glycosylation sites. It also contains domains consistent with other class A plexins including a Sema domain, three "Met-related sequences"/cysteine clusters, three extracellular glycine-proline repeats, intracellular SP domains, and a putative intracellular tyrosine kinase phosphorylation site.