Integrin alphaV, beta8, Recombinant, Human

Integrin avb8 is one of five av integrins and the only known b8 integrin. 1-3 The non-covalent heterodimer of 170 kD av and ~90 kD b8 integrin type I transmembrane glycoprotein subunits is expressed in yolk sac, placenta, brain perivascular astrocytes, Schwann cells, renal glomerular mesangial cells and pulmonary epithelial cells. 3-7 Unlike other av integrins, avb8 does not appear to assume different activation states, and the cytoplasmic tail does not connect to the cytoskeleton. 3, 8 It binds ligands containing an RGD motif, including vitronectin, fibrin and the latency associated peptide (LAP) of the latent TGF-b complex. 7-12 High affinity binding of avb8 to LAP allows proteolytic cleavage by MT1-MMP, which releases active TGF-b. This mechanism differs from that of avb6, the other av integrin which can activate TGF-b from latency through non-proteolytic mechanisms. 13 Downstream effects of TGF-b activation include control of cell growth and associated vascularization. 10-13 Deletion of either av or b8 reveals that avb8 is required for vascular morphogenesis in the embryonic brain and yolk sac. 4, 14, 15 The 962 aa human av extracellular domain (ECD) shares 92-95% aa sequence identity with mouse, rat and cow av, while the 642 aa human b8 ECD shares 92%, 92%, 89%, 87% and 87% aa identity with cow, dog, rabbit, mouse and rat b8, respectively. The b8 ECD of b8 shows low (~35%) aa identity with other integrin b subunits, and the cytoplasmic tail is unlike any other integrin. The av ECD contains an N-terminal b- propeller structure, followed by domains termed thigh, calf-1 and calf-2. 1 The b8 ECD contains a vWFA domain, which interacts with the avb-propeller to form a binding domain. Each subunit has a transmembrane sequence and a short cytoplasmic tail.\n\nSource: Human CD33 Signal Peptide (Met 1-Ala 16), Human Integrin aV (Phe 31-Val 992) acidic tail, Human CD33 Signal Peptide (Met 1-Ala 16), Human Integrin b8 (Glu 43-Arg 684) basic tail; DNA sequences encoding the extracellular domain of human Integrin aV (Phe 31-Val 992; Accession # P06756) (Suzuki, S. et al., 1987, J. Biol. Chem. 262:14080-085) with an acid tail at the C-terminus and the extracellular domain of human Integrin b8 (Glu 43-Arg 684; Accession # P26012) (Moyle, M. et al., 1991, J. Biol. Chem 266:19650-658) with a basic tail at the C-terminus were cloned downstream of the human CD33 signal peptide and co-expressed in CHO cells.\n\nMolecular Mass: Based on N-terminal sequencing, the recombinant human Integrin aV subunit starts at Phe 31 and has a calculated molecular mass of approximately 111 kD. The b8 subunit starts at Glu 43 and has a calculated molecular mass of approximately 75.3 kD. As a result of glycosylation, the recombinant proteins migrate as approximately 130-155 and 85-100 kD protein bands in SDS-PAGE under reducing conditions.\n\nEndotoxin Level: < 1.0 EU per 1 microg of the protein as determined by the LAL method.\n\nActivity: Measured by its ability to bind rhLap. When rhIntegrin aVb8 is coated at 0.1ug/ml, rhLap binds with an apparent KD < 0.5 nM.\n\nReconstitution: It is recommended that sterile PBS be added to the vial to prepare a working stock solution of no less than 100ug/ml. The carrier-free protein should be used immediately upon reconstitution to avoid losses in activity due to non-specific binding to the inside surface of the vial. For long term storage as a dilute solution, a carrier protein (e.g. 0.1% HSA or BSA) should be added to the vial.\n\nStorage and Stability: Lyophilized samples are stable for up to twelve months at -20 degrees C. Upon reconstitution, this protein, in the presence of a carrier protein, can be stored under sterile conditions at 2 degrees -8 degrees C for one month or at -20 degrees C in a manual defrost freezer for three months without detectable loss of activity. Avoid repeated freeze-thaw cycles.

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SPECIFICATIONS

Catalog Number

I7661-37X8

Size

50ug

Form

Supplied as a lyophilized powder in 50mM Tris, 150mM NaCl and 2mM MgCl2, pH 7.4.

Purity

(same/more than) 90%, as determined by SDS-PAGE and visualized by silver stain.

References

1. Hynes, R. O., 2002, Cell 110:673. \n2. Suzuki, S. et al., 1987, J. Biol. Chem. 262:14080. \n3. Moyle, M. et al., 1991, J. Biol. Chem. 266:19650. \n4. Zhu, J. et al., 2002, Development 129:2891. \n5. Cambier, S. et al., 2000, Cancer Res. 60:7084. \n6. Lakhe-Reddy, S. et al., 2006, J. Biol. Chem. 281:19688. \n7. Chernousov, M. A. and D. J. Carey, 2003, Exp. Cell Res. 291:514. \n8. Nishimura, S. L. et al., 1994, J. Biol. Chem. 269:28708. \n9. Milner, R. et al., 1999, J. Cell Sci. 112:4271. \n10. Cambier, S. et al., 2005, Am. J. Pathol. 166:1883. \n11. Fjellbirkeland, L. et al., 2003, Am. J. Pathol. 163:533. \n12. Araya, J. et al., 2006, Am. J. Pathol. 169:405. \n13. Mu, D. et al., 2002, J. Cell Biol. 157:493. \n14. Proctor, J. M. et al., 2005, J. Neurosci. 25:9940. \n15. McCarty, J. H. et al., 2005, Development 132:165.