Rabbit Antibody to FAPα (Fibroblast Activation Protein alpha subunit, Seprase, Integral Membrane Serine Protease) Catalytic Insert

RP4-FAPα is a rabbit polyclonal antibody made to the Type-II serine protease FAPα.. The antibody is made to a synthetic peptide based on the insert in the catalytic domain of human FAPα.  RP4- FAPα  reacts with human, mouse and rat FAPα, and does not recognize other DPP family members. The antibody has been peptide-affinity purified, concentrated to 1.0 mg/ml, with the addition of 0.05% sodium azide as preservative and 50% glycerol as cryoprotectant.

FAPα (Fibroblast Activation Protein alpha subunit) is the alpha subunit and DPP-IV the beta subunit of a heterodimeric membrane–bound proteinase complex. Also known as 170 kDa Melanoma Membrane Gelatinase, Integral Membrane Serine Proteinase and Seprase, FAPα was first identified as a membrane glycoprotein of fibroblasts and tumor cells, in a search for tumor cell markers. The beta subunit of the complex was identified as dipeptidyl peptidase-4 (DPP-IV), also known as CD26. Not all cells and tissues make the heterodimer; some make only FAPα homodimers, some only DPP-4 homodimers. It has been reported that CD26/ FAPα  colocalizes  with UPAR in melanoma cells, that larger complexes form with integrins and other connective tissue components, and that this impacts cell migration.  Also reported is that FAPα is produced by over 90% of human epithelial cancers, expressed by the stromal fibroblasts. FAPα also is reported to promote tumor growth and angiogenesis in breast cancer model systems. FAPα at the edges of invadipodia  is thought to aid in cell migration and ECM/connective tissue breakdown. FAPα is considered a dual-function proteinase, acting both as a dipeptidyl peptidase and as a collagenase, although there is some debate as to specificity. The clan SC proteinases have a catalytic triad of Ser-Asp-His, and like other Serine proteinases, the active site serine is in a Gly-Xaa-Ser-Xaa-Gly orientation. FAPα is a member of a broader family of dipeptidyl peptidases including DPP-4, DPP-2, DPP-8, DPP-9, DPP-10, which have differing substrate specificities and tissue localizations. The surface-bound FAPα is shed from cells, and cleavage of the stalk region releases the shed form found in serum. Two human FAPα have been reported, 759 and 760 amino acids in length, with predicted mass of 87.7  and 87.8 kDa, and pI of 6.2 and 6.45 respectively. Postranslational modifications and reduction lead to an apparent mass of 110-120 kDa on SDS-PAGE gels. The 759 amino acid sequence has an insertion in the catalytic domain, but retains the catalytic triad. It is not clear what functional difference the two isoforms have. This FAPα antibody recognizes the 759 amino acid form specifically. There also is reported a much shorter sequence encoding only the carboxyterminal portion of FAPα, only the catalytic domain. A recommended starting concentration for Western blots is 1:1,000 when using colorimetric substrates such as BCIP/NBT, and 1:5,000 for chemiluminescent substrates.  Higher concentrations of antibody may be needed for samples from more distantly related species.  EDTA/EGTA treatment of tissues or lysates is required to see latent zymogen.

FOR RESEARCH USE ONLY. NOT FOR USE IN HUMANS.

The undiluted antibody solution is stable for 12 months at -20°C.

Triple Point Biologics products are sold exclusively through Abcam. For availability, pricing and buying information please select your country below and press 'Go'. You will be relocated to the relevant datasheet page on Abcam's website.