| Semaphorin 5A (Sema5A, previously called SemaF) is a 140kD protein of the semaphorin family of axon guidance molecules (1-4). Class 5 semaphorins are type I transmembrane glycoproteins with an N-terminal Sema domain and multiple juxtamembrane type 1 thrombospondin (TSP) repeats within their extracellular domains (1-3). Sema5A is expressed developmentally in oligodendrocytes, neuroepithelial cells surrounding retinal axons, the base of limb buds, the cardiac atrial septum and endocardial cushions, and the mesoderm surrounding cranial vessels (3-6). The mouse Sema5A cDNA encodes a 22aa signal sequence, a 946 aa extracellular domain (ECD), a 24 aa transmembrane sequence and an 85 aa cytoplasmic portion. Within aa 23-765, which includes the sema domain and four of the seven TSP repeats, mouse Sema5A shares 93%, 98%, 93%, 92% and 91% aa identity with corresponding human, rat, porcine, bovine and canine sequences. Semaphorins typically transduce signals through transmembrane plexins (1, 2). The sema domain of Sema5A binds plexin B3, triggering signaling via HGF R/c-Met (7). Both Sema5A and plexin B3 are expressed postnatally during differentiation and migration of central nervous system oligodendrocytes. However, plexin B3 is not significantly expressed prenatally and therefore unlikely to be the Sema5A receptor during development (7, 8). The Sema5A TSP repeats interact with either heparin sulfate or chondroitin sulfate proteoglycans (HSPG, CSPG) (9). HSPG interaction promotes attraction, while CSPG interaction promotes repulsion and is essential for axon fasciculation, independent of plexin B3 (9, 10). Sema5A mutations have been implicated in the human genetic syndrome, cri-du-chat, while some polymorphisms may increase risk for neurodegenerative diseases such as Parkinsons (11, 12). Sema5A expression may be up-regulated in metastatic cancer cells and down-regulated in autism (13, 14). High expression of Sema5A has been associated with tumor growth and metastasis in pancreatic cancer (15). Source: Recombinant corresponding to mouse Semaphorin 5A Fc Chimera (Met1-Thr765) at N-terminus and Mouse IgG2A (Glu98-Lys330) at C-terminus, expressed in CHO cells. Molecular Weight: ~110.8kD Endotoxin Level: 1EU/1ug (LAL) Biological Avtivity: Measured by the ability of the immobilized protein to support the adhesion of MIA PaCa-2 human pancreatic cancer cells (ATCC: CRL-1420). The ED50 for this effect is typically 0.9-3.6ug/ml. Storage and Stability: Lyophilized powder may be stored at -20C. Stable for 12 months at -20C. Reconstitute with PBS. Aliquot to avoid repeated freezing and thawing. Store at -20C. Reconstituted product is stable for 6 months at -20C. For maximum recovery of product, centrifuge the original vial after thawing and prior to removing the cap. Further dilutions can be made in assay buffer. |
