P-selectin is the largest of the known selectins at 140kDa. It contains nine consensus repeats (CR) and extends approximately 40 nm from the endothelial surface. Other names for P-selectin include CD62P, Granule Membrane Protein 140 (GMP-140), and Platelet Activation-Dependent Granule to External Membrane Protein (PADGEM). P-selectin is expressed in a-granules of activated platelets and granules of endothelial cells.

Within minutes of stimulation of the endothelial cells by inflammatory mediators such as histamine, thrombin, or phorbol esters, P-selectin is surface-expressed. Expression of P-selectin also occurs from the surgical trauma endured during preparation of the tissues for intravital microscopy. The expression is short-lived, reaching its peak after only ten minutes. Additional synthesis of P-selectin is brought about within two hours by cytokines such as interleukin-1 (IL-1) or tumor necrosis factor a (TNF-a). The primary ligand for P-selectin is PSGL-1 (P-selectin glycoprotein ligand-1) which is constitutively found on all leukocytes. Other ligands for P-selectin include CD24 and uncharacterized ligands. The transient interactions between P-selectin and PSGL-1 allow leukocytes to roll along the venular endothelium. Accordingly, P-selectin is largely responsible for the rolling phase of the leukocyte adhesion cascade. P-selectin can also mediate capture when L-selectin is not present.

Several experiments in mice have illustrated the pertinent role of P-selectin in leukocyte rolling. In mice deficient for P-selectin, trauma-induced rolling is absent immediately, but returns after 1-2 hours. In this case, the delayed rolling is L-selectin dependent, but the leukocytes roll much faster than in wild-type mice, suggesting that L-selectin cannot independently support rolling at typical in vivo velocities. On the other hand, in L-selectin deficient mice, P-selectin mediates most trauma-induced leukocyte rolling. Normal leukocyte rolling is seen for approximately 90 minutes, showing that P-selectin has the ability to capture leukocytes from the bloodstream and start them rolling along the endothelium even without the presence of L-selectin.

In TNF-a -stimulated venules, P-selectin and E-selectin tend to have overlapping functions. In mice deficient for P-selectin, it is necessary to block E-selectin function to significantly reduce rolling, and in E-selectin knockouts, an antibody against P-selectin must be introduced to reduce rolling. Correspondingly, no leukocyte rolling is observed in E-selectin/P-selectin double deficient mice treated with TNF-a. Although P- and E-selectin seem to have redundant functions, observations of rolling flux fraction and rolling velocity indicate that P-selectin is responsible for early rolling while E-selectin allows slow rolling and more adhesion.

Representative 3-D Structure of P-Selectin: only the EGF domain of P-selectin. Also available is a theoretical 3-D model of P-selectin (the C-type lectin domain, and residues 1-120). These 3-D structures are viewed using RasMol. Left-clicking on the molecule allows change in orientation, and right-clicking on the molecule gives options for different display modes.

View various information about this molecule at the National Center for Biotechnology Information.


Search similar protein and nucleotide sequences between various species using BLAST (Basic Local Alignment Search Tool)
  • Copy the desired sequence from the GenBank Database and paste it into the text box on the BLAST page.
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Read the following categorized abstracts or link to Medline to conduct your own query.

  • Cloning of the human gene: Cloning of GMP-140, a granule membrane protein of platelets and endothelium: sequence similarity to proteins involved in cell adhesion and inflammation.
  • Cloning of the murine gene: Cloning of the mouse endothelial selectins. Expression of both E- and P-selectin is inducible by tumor necrosis factor.
  • Potential disease relevance: P- and E-selectin mediate recruitment of T-helper-1 but not T-helper-2 cells into inflammed tissues.
  • Microcirculation-based publication: Sequential contribution of L- and P-selectin to leukocyte rolling in vivo.
  • First knockout mouse: Leukocyte rolling and extravasation are severely compromised in P selectin-deficient mice.

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