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

As selectinas são glicoproteínas da superfície celular que se ligam a ligantes de carboidratos e participam da adesão célula a célula transitória.
Todas as selectinas compreendem um domínio de lectina N-terminal e um fator de crescimento epidérmico ou domínio EGF que regulam a especificidade e a força de ligação.
No entanto, o número de repetições conservadas por sequência ou domínios SCR pode variar de duas a nove repetições, dependendo do tipo de selectina.
As L-selectinas curtas expressas em células imunes como linfócitos as ajudam a migrar para os gânglios linfáticos, ligando ligantes nas células endoteliais.
As P-selectinas maiores são expressas principalmente nas plaquetas. Eles ajudam a agregar plaquetas e células imunológicas no local da lesão.
Um terceiro tipo, chamado E-selectinas, é temporariamente expresso junto com P-selectinas nas células endoteliais durante uma resposta imune.
Essas selectinas formam interações fracas e transitórias com leucócitos de fluxo livre e os retardam.
Os leucócitos então rolam ao longo da superfície endotelial, onde outras moléculas de adesão celular ajudam a recrutá-los para os microambientes de tecido apropriados - um processo chamado homing de leucócitos.

<ol>
	<li>"Selectinas na imunidade ao câncer." Glicobiologia 28.9 (2018): 648-655.</li>
	<li>Gota, Stéphanie, Pierre-Luc Tremblay e Jacques Huot. "Selectinas e ligantes de selectina no extravasamento de células cancerígenas e seletividade de órgãos de metástase." Metástase clínica e experimental 25.4 (2008): 335-344.</li>
</ol>

selectinas

Selectins

A adesão celular é um aspecto essencial da multicelularidade. Embora as interações celulares estáveis geralmente ocorram entre células do mesmo tipo, as interações celulares transitórias ocorrem entre células de diferentes tipos de tecidos, como entre neutrófilos e células endoteliais. As selectinas são uma classe de moléculas de adesão celular (CAMs) que se ligam a ligantes de carboidratos para formar adesão celular transitória. Elas são proteínas em forma de bastonete com uma longa parte extracelular de comprimento variável terminando com o domínio de lectina, que é uma lectina do tipo C que se liga a carboidratos apenas na presença de íons de cálcio. Três tipos principais de selectinas são identificados com base na sua especificidade e comprimento do tecido – L-selectinas, P-selectinas e E-selectinas. Selectinas na resposta imunológica As células endoteliais que revestem os vasos sanguíneos expressam selectinas P e as armazenam em corpos vesiculares chamados corpos de Weible-Palade. Durante a inflamação, a estimulação da histamina mobiliza rapidamente estas vesículas para a superfície celular. Estas células endoteliais ativadas também regulam positivamente os seus genes E-selectina e P-selectina, preparando-as assim para recrutar leucócitos de fluxo livre a partir da corrente sanguínea. Os leucócitos, como os neutrófilos e os eosinófilos, expressam os ligantes de carboidratos, como o PSGL-1, na superfície celular. As longas selectinas que se projetam das células endoteliais podem interagir facilmente com esses ligantes e "capturar" os leucócitos que fluem livremente da corrente sanguínea. As selectinas estão inicialmente na conformação fechada e, portanto, ligam-se fracamente aos seus ligantes. No entanto, à medida que o leucócito flui, a tensão de cisalhamento dessas interações desencadeia a abertura das selectinas. As selectinas em conformação aberta podem ligar-se fortemente aos seus ligantes e, assim, ajudar a desacelerar os leucócitos. Selectinas no Câncer As células cancerígenas metastáticas sequestram o processo normal de recrutamento mediado pela selectina para invadir tecidos saudáveis. Estas células metastáticas expressam os ligandos de hidratos de carbono na sua superfície celular e assim tornam-se receptivas para se ligarem às células endoteliais. Após a ligação, as células cancerígenas podem escapar do vaso sanguíneo através de um processo denominado extravasamento. As células cancerosas podem então infiltrar-se no novo local, produzindo tumores secundários.

Selectinas

A adesão celular é um aspecto essencial da multicelularidade. Embora as interações celulares estáveis geralmente ocorram entre células do mesmo tipo, transientes ...

Education

JoVE Core

Cell Biology

Biologia Celular

Unit 1

Unidade 1

Cell-Cell Interactions

Interações Célula-Célula

KEY TERMS AND CONCEPTS

TERMOS-CHAVE E CONCEITOS

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

cell adhesion molecules - types and functions

cell-adhesion-molecules-types-and-functions

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Cell adhesion molecules help cells stick together and work as part of a tissue. They give multicellular organisms physical strength and also help cells send signals across the plasma membrane. These proteins are important for coordinated activity in tissues and organ systems. CAMs are grouped into four main families: integrins, cadherins, selectins, and immunoglobulin-like CAMs, or IgCAMs. Each family supports cell interactions in a different way. Some CAMs help cells attach firmly, while...

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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...

immunoglobulin-like cell adhesion molecules

immunoglobulin-like-cell-adhesion-molecules

Ig-CAMs in Neural Growth and Disease

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overview of cell-cell junctions

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adherens junctions

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Adherens junctions are strong cell-to-cell anchors that help tissues stay connected. These anchoring junctions work with desmosomes, another type of junction that holds adjacent cells together. In many epithelial and endothelial tissues, adherens junctions form a continuous adhesion belt. In heart muscle, they often appear as clusters that help cells work together for coordinated contraction. Adherens junctions are also dynamic, especially in the cells that line blood vessels. These...

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Adherens junctions help cells stay attached while they respond to mechanical force. These multi-protein complexes can adapt to tensile force and shear stress. When the force changes, mechanosensory proteins in the junction can change shape. This process is called mechanotransduction. Alpha-catenin is one of the main force-sensing proteins in adherens junctions. It is an allosteric protein, which means its shape affects how it works. Alpha-catenin has three VH, or vinculin homology, domains...

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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 - Biologia Celular ilustra processos celulares complexos em vídeos de animação fáceis de entender e, ao mesmo tempo, abrangentes. Esta coleção foca nos componentes e funções essenciais das células, incluindo organelas e membranas, transporte celular e energia celular. É complementado por vídeos de Cientistas em ação que demonstram a aplicação da biologia celular em experimentos de pesquisa do mundo real.

Selectins in Immune Cell Capture

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