Name: selectins in immune cell capture
Uploaded: 2023-04-30T11:56:02.000Z
Duration: 1 min 25 s
Channel: JoVE

Les sélectines sont des glycoprotéines de surface cellulaire qui se lient aux ligands glucidiques et participent à l’adhésion transitoire entre les cellules.
Toutes les sélectines comprennent un domaine de lectine N-terminal et un facteur de croissance épidermique ou domaine EGF qui régulent la spécificité et la force de liaison.
Cependant, le nombre de répétitions conservées en séquence ou de domaines SCR peut varier de deux à neuf répétitions selon le type de sélectine.
Les L-sélectines courtes exprimées sur les cellules immunitaires comme les lymphocytes les aident à migrer dans les ganglions lymphatiques en liant des ligands sur les cellules endothéliales.
Les P-sélectines plus grandes sont principalement exprimées sur les plaquettes. Ils aident à agréger les plaquettes et les cellules immunitaires sur le site de la lésion.
Un troisième type, appelé E-sélectines, est exprimé temporellement avec les P-sélectines sur les cellules endothéliales au cours d’une réponse immunitaire.
Ces sélectines forment des interactions faibles et transitoires avec les leucocytes à écoulement libre et les ralentissent.
Les leucocytes roulent ensuite le long de la surface endothéliale, où d’autres molécules d’adhésion cellulaire aident à les recruter dans les microenvironnements tissulaires appropriés - un processus appelé guidage leucocytaire.

<ol>
	<li>Borsig, Lubor. « Sélectines dans l’immunité contre le cancer. » Glycobiologie 28.9 (2018) : 648-655.</li>
	<li>Gout, Stéphanie, Pierre-Luc Tremblay et Jacques Huot. « Sélectines et ligands sélectifs dans l’extravasation des cellules cancéreuses et la sélectivité des métastases pour les organes. » Métastases cliniques et expérimentales 25.4 (2008) : 335-344.</li>
</ol>

sélectines

Selectins

L'adhésion cellulaire est un aspect essentiel de la multicellularité. Alors que des interactions cellulaires stables se produisent généralement entre des cellules du même type, des interactions cellulaires transitoires se produisent entre des cellules de différents types de tissus, par exemple entre les neutrophiles et les cellules endothéliales. Les sélectines sont une classe de molécules d'adhésion cellulaire (CAM) qui se lient aux ligands glucidiques pour former une adhésion cellulaire transitoire. Ce sont des protéines en forme de bâtonnet avec une longue partie extracellulaire de longueur variable se terminant par le domaine lectine, qui est une lectine de type C qui se lie aux glucides uniquement en présence d'ions calcium. Trois principaux types de sélectines sont identifiés en fonction de leur spécificité tissulaire et de leur longueur : les sélectines L, les sélectines P et les sélectines E.

Sélectines dans la Réponse Immunitaire

Les cellules endothéliales tapissant les vaisseaux sanguins expriment les sélectines P et les stockent dans des corps vésiculaires appelés corps de Weible-Palade. Lors d’une inflammation, la stimulation par l’histamine mobilise rapidement ces vésicules à la surface cellulaire. Ces cellules endothéliales activées régulent également positivement leurs gènes de sélectine E et de sélectine P, les incitant ainsi à recruter des leucocytes à écoulement libre dans la circulation sanguine.

Les leucocytes, tels que les neutrophiles et les éosinophiles, expriment les ligands glucidiques, tels que le PSGL-1, à la surface de leurs cellules. Les longues sélectines dépassant des cellules endothéliales peuvent facilement interagir avec ces ligands et « attraper » les leucocytes libres de la circulation sanguine. Les sélectines sont initialement en conformation fermée et se lient donc faiblement à leurs ligands. Cependant, à mesure que les leucocytes circulent, la contrainte de cisaillement de ces interactions déclenche l’ouverture des sélectines. Les sélectines en conformation ouverte peuvent se lier fortement à leurs ligands et ainsi aider à ralentir les leucocytes.

Sélectines dans le Cancer

Les cellules cancéreuses métastatiques détournent le processus de recrutement normal médié par la sélectine pour envahir les tissus sains. Ces cellules métastatiques expriment les ligands glucidiques à la surface de leurs cellules et deviennent ainsi réceptives pour se lier aux cellules endothéliales. Une fois liées, les cellules cancéreuses peuvent s’échapper du vaisseau sanguin, grâce à un processus appelé extravasation. Les cellules cancéreuses peuvent alors infiltrer le nouveau site, produisant des tumeurs secondaires.

Sélectines

L’adhésion cellulaire est un aspect essentiel de la multicellularité. Alors que des interactions cellulaires stables se produisent généralement entre des cellules du même type, les ...

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selectins in immune cell capture

Selectins help cells make short, temporary contacts during immune responses. They are cell adhesion molecules that bind carbohydrate ligands on other cells. These rod-like proteins have a long outside region and end in a lectin domain, which binds carbohydrates only when calcium ions are present.

Three main selectins are known: L-selectin, P-selectin, and E-selectin. Their names reflect where they are found and how long they are. This tissue specificity helps explain why selectins act in certain cell interactions instead of making permanent attachments.

In blood vessels, endothelial cells line the vessel wall and use selectins to recruit leukocytes during inflammation. These cells store P-selectin in vesicular bodies called Weibel-Palade bodies. When histamine stimulates the cells, the vesicles move quickly to the cell surface. The activated endothelial cells also increase E-selectin and P-selectin gene expression, which prepares them to attract free-flowing leukocytes.

Leukocytes such as neutrophils and eosinophils carry carbohydrate ligands on their surface, including PSGL-1. Long selectins on endothelial cells can reach out and catch these moving cells from the bloodstream. Selectins start in a closed form, so they bind weakly at first. As the leukocyte keeps moving, shear stress from the interaction opens the selectin. In the open form, the selectin binds more strongly and slows the leukocyte down.

Cancer cells can also use this same pathway. Metastatic cancer cells display carbohydrate ligands on their surface and can bind endothelial cells. This lets them leave the blood vessel by extravasation and enter a new tissue. Once there, they can grow into secondary tumors.

Selectins in Immune Cell Capture

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selectins

Selectins help cells make short, temporary contacts during immune responses. They are cell adhesion molecules that bind carbohydrate ligands on other cells. These rod-like proteins have a long outside region and end in a lectin domain, which binds carbohydrates only when calcium ions are present. Three main selectins are known: L-selectin, P-selectin, and E-selectin. Their names reflect where they are found and how long they are. This tissue specificity helps explain why selectins act in...

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key terms and concepts

Learn how selectins help leukocytes slow down, how inflammation activates endothelial cells, and how metastatic cancer cells use the same pathway.

Selectins in Immune Cell Capture | JoVE K12

cell biology

JoVE Core Biologie cellulaire illustre les processus cellulaires complexes dans des leçons vidéos complètes mais faciles à comprendre. Cette collection se concentre sur les composants et fonctions essentiels de la cellule ; cela inclut les organelles et les membranes ainsi que le transport et le métabolisme énergétique cellulaire. Elle est complétée par nos vidéos de scientifiques à l'action qui démontrent l'application de la biologie cellulaire dans des expériences concrètes.

Selectins in Immune Cell Capture

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