Cell Adhesion and Signalling Overview
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Questions and Answers

Selectins are regulated by ______ mediators

inflammatory

Hemidesmosomes link extracellular laminin in the basement membrane to ______ within epithelial cells

keratins

Integrins are a family of adhesion molecules that are ______ bound heterodimers

non-covalently

Desmosomes and adherens junctions involve proteins that connect to the ______ cytoskeleton

<p>actin</p> Signup and view all the answers

The ______ superfamily includes proteins important for cell adhesion and immune response

<p>immunoglobulin</p> Signup and view all the answers

Integrins are involved in the attachment of epithelial cells to the ______.

<p>basal lamina</p> Signup and view all the answers

In the absence of ligand, integrin dimers adopt a ______ structure.

<p>folded</p> Signup and view all the answers

Talin can activate integrins through ______-out signaling.

<p>inside</p> Signup and view all the answers

The extracellular portion of integrins adopts an extended conformation to achieve higher ______ for ligand.

<p>affinity</p> Signup and view all the answers

Focal adhesions are specialized structures involved in cell-matrix ______.

<p>adhesion</p> Signup and view all the answers

Gap junctions function primarily in ______ communication between cells.

<p>direct</p> Signup and view all the answers

Selectins play a crucial role in mediating ______ response during inflammation.

<p>immune</p> Signup and view all the answers

Catenins link cadherins to the ______ network inside the cell.

<p>actin</p> Signup and view all the answers

Cadherins are a family of adhesion proteins which mediate Ca2+ dependent ______ adhesion.

<p>homophilic</p> Signup and view all the answers

Catenins link classical cadherins to the ______ cytoskeleton.

<p>actin</p> Signup and view all the answers

Gap junctions enable small molecule transfer including inorganic ions, sugars, and ______.

<p>amino acids</p> Signup and view all the answers

The T cell receptor is an Ig family ______ molecule.

<p>adhesion</p> Signup and view all the answers

Selectins are cell surface carbohydrate binding proteins that are ______ dependent.

<p>Ca2+</p> Signup and view all the answers

Transient, weak interactions between selectins on endothelial cells and carbohydrate ligands on ______ allow the cells to attach to blood vessel walls.

<p>neutrophils</p> Signup and view all the answers

Immunoglobulin superfamily members can be either homophilic or ______ in their adhesion capabilities.

<p>heterophilic</p> Signup and view all the answers

In the immune response, PECAM is found on platelets and ______ cells.

<p>endothelial</p> Signup and view all the answers

The cadherin extracellular domains link together to mediate ______.

<p>adhesion</p> Signup and view all the answers

Integrins mediate tight binding and migration into connective ______.

<p>tissue</p> Signup and view all the answers

Cadherins form junctions that are individually low affinity but combine to give strong ______.

<p>attachment</p> Signup and view all the answers

Tight junctions are important for maintaining ______ integrity in epithelial layers.

<p>barrier</p> Signup and view all the answers

Gap junctions also facilitate the transfer of ______ signaling molecules between cells.

<p>intracellular</p> Signup and view all the answers

Cadherins require ______ for their function, which is crucial for cell adhesion.

<p>calcium</p> Signup and view all the answers

What structural change occurs in integrin dimers after activation by ligand binding?

<p>The dimer breaks interaction between cytoplasmic tails.</p> Signup and view all the answers

What is the role of talin in the inside-out signaling mechanism of integrin activation?

<p>Talin competes for binding with cytoplasmic tails to activate integrins.</p> Signup and view all the answers

Which of the following describes the function of focal adhesions in motile cells?

<p>They serve as anchorage points for F-actin and integrins.</p> Signup and view all the answers

Which factor is involved in the activation of integrins in response to chemokine receptor activation?

<p>PIP2 signaling.</p> Signup and view all the answers

What effect does ligand binding have on the conformation of integrins?

<p>It results in an extended conformation with higher ligand affinity.</p> Signup and view all the answers

What is the primary role of cell adhesion molecules in multicellular organisms?

<p>They facilitate the attachment of cells to each other and the extracellular matrix.</p> Signup and view all the answers

Which type of junction primarily seals gaps between epithelial cells to maintain permeability?

<p>Tight junctions</p> Signup and view all the answers

What type of adhesion is primarily involved in the transient binding of leukocytes to endothelial cells?

<p>Selectins</p> Signup and view all the answers

Which family of proteins links to the actin cytoskeleton and plays a key role in adherens junctions?

<p>Cadherins</p> Signup and view all the answers

Which junction allows the passage of small molecules and ions between the cytoplasm of adjacent cells?

<p>Gap junctions</p> Signup and view all the answers

What is the primary function of integrins in cell adhesion?

<p>Connecting epithelial cells to the extracellular matrix.</p> Signup and view all the answers

Which type of junction provides mechanical strength and resistance to stress in tissues like the skin?

<p>Desmosomes</p> Signup and view all the answers

What type of signaling occurs at the sites of cell-cell contact formed by cell adhesion molecules?

<p>Signal transduction that can regulate various cellular activities.</p> Signup and view all the answers

What role do selectins play in the body during inflammation?

<p>They facilitate neutrophil extravasation.</p> Signup and view all the answers

Which of the following statements correctly describes syndecans?

<p>They aid in cell adhesion to the extracellular matrix.</p> Signup and view all the answers

What is a unique characteristic of hemidesmosomes?

<p>They link laminin to keratin in epithelial cells.</p> Signup and view all the answers

How do integrins contribute to cellular function?

<p>They connect the extracellular matrix to the intracellular cytoskeleton.</p> Signup and view all the answers

Which type of adhesion do selectins primarily mediate?

<p>Transient interactions between leukocytes and endothelium.</p> Signup and view all the answers

What is the function of plectin and dystonin in hemidesmosomes?

<p>They act as linker proteins connecting integrins to keratins.</p> Signup and view all the answers

Which type of cell adhesion is primarily associated with cadherins?

<p>Strong adhesive junctions that require calcium ions.</p> Signup and view all the answers

What cellular response increases the expression of E-selectin on vascular endothelial cells?

<p>Response to inflammatory mediators.</p> Signup and view all the answers

Which statement best describes integrin function?

<p>Integrins assist in cell adhesion to the extracellular matrix.</p> Signup and view all the answers

What is the primary role of selectins during an inflammatory response?

<p>Mediating leukocyte rolling and adhesion.</p> Signup and view all the answers

What is the role of catenins in relation to cadherins?

<p>They link classical cadherins to the actin cytoskeleton.</p> Signup and view all the answers

What distinguishes the immunoglobulin superfamily from cadherins?

<p>Immunoglobulin superfamily has multiple Ig-like domains.</p> Signup and view all the answers

How do cadherins achieve strong attachment despite their individual low affinity?

<p>By combining multiple adhesion events.</p> Signup and view all the answers

Which type of molecules can gap junctions transfer between cells?

<p>Nucleotides and cyclic AMP</p> Signup and view all the answers

What is a primary function of cadherins in embryonic development?

<p>Mediating cell segregation.</p> Signup and view all the answers

Which component does L-selectin interact with for lymphocyte homing?

<p>Vascular addressins</p> Signup and view all the answers

What is indicated by the presence of multiple Ig-family adhesion molecules during immune responses?

<p>A diverse range of adhesion and signaling capabilities.</p> Signup and view all the answers

What role do tight junctions play in epithelial tissue?

<p>Creating a selective barrier for molecule transport.</p> Signup and view all the answers

Which characteristic is specific to integrins compared to cadherins?

<p>Integrins are bound heterodimers.</p> Signup and view all the answers

Study Notes

Cell Adhesion and Cell Signalling

  • Multicellular organisms rely on cell adhesion to each other and the extracellular matrix (ECM) for tissue formation.
  • Some adhesive interactions are stable, like those between muscle cells and connective tissue in tendons for force transmission, or skin epithelial cells to prevent abrasion.
  • Other cellular adhesions are transient, such as leukocytes binding to endothelial cells for extravasation into tissues, or cell attachment to the ECM during migration.

Cell Junctions

  • Cell-cell junctions (adherens junctions, desmosomes), and cell-matrix adhesions (actin-linked, or hemidesmosomes) connect to the cytoskeleton and transmit physical forces.
  • Tight junctions (septate junctions) seal gaps between epithelial cells, controlling permeability.
  • Gap junctions allow small molecules and ions to pass between cells, facilitating signal transduction.

Cellular Adhesion Molecules

  • Cadherins link cells to cells and mediate Ca2+ dependent homophilic adhesion.
  • Integrins link cells to the extracellular matrix (ECM) and mediate adhesion of cells to the ECM.
  • Selectins mediate interactions between cells, particularly important in immune functions.
  • Immunoglobulin (Ig) superfamily members exhibit Ca2+ independent adhesion, playing important roles in various cell interactions.

Cell-Cell Adhesion at a Synapse

  • Synapse formation requires multiple adhesion molecules to join pre- and post-synaptic membranes.
  • This process anchors components of signalling machinery firmly, thereby localising neurotransmitter actions.

Selectins

  • Selectins are cell-surface carbohydrate-binding proteins that bind to mucin-type glycoproteins.
  • Their function is Ca2+-dependent and is essential for binding to white blood cells, platelets, and endothelial cells.

Cell Adhesion Molecules in Lymph Nodes

  • Lymphocytes bind to vascular endothelium in lymph nodes via interactions between L-selectin and vascular addressins.

Cell Adhesion Molecules and Neutrophil Recruitment

  • Selectin-mediated adhesion is weak, enabling neutrophils to roll along blood vessels.
  • Transient, weak interactions allow cells to attach to blood vessel walls.
  • Other adhesion molecules regulate tight binding and migration into infected tissue.

Regulation of Selectins

  • Selectins are responsive to inflammatory mediators, like TNFα, CXCL8, leukotriene LTB4, histamine, and thrombin.
  • These mediators induce upregulation of E-selectins on vascular endothelial cells, facilitating neutrophil extravasation.

Syndecans

  • Syndecans are cell-surface proteoglycans that are expressed on many cell types, mediating cell adhesion to the extracellular matrix and binding growth factors like FGF.

Desmosomes

  • Desmosomes are cell-cell junctions. They are formed by non-classical cadherin proteins and intermediate filaments.

Hemidesmosomes

  • Hemidesmosomes are anchoring junctions. They link cells to the basal lamina via integrins that connect to keratins within epithelial cells.

Integrin Mediated Adhesions

  • Integrins mediate various cell-cell and cell-matrix adhesions through different types of adhesion structures (focal adhesions and podosomes).

Integrin Activation

  • Integrins can exist in active or inactive states, controlled by outside-in or inside-out signalling.

Integrin Pairs

  • Integrins are heterodimeric transmembrane proteins playing vital roles in cell-cell and cell-matrix adhesion. They exhibit variability across different cell types/tissues.

Integrin Ligands

  • Various extracellular matrix proteins serve as ligands for integrins, influencing cell adhesion and migration.

Integrins in Cell-Cell Adhesion

  • Integrins can bind to other cellular adhesion molecules like those in the Ig family, potentially strengthening the interaction.

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Cell Adhesion and Cell Signalling PDF

Description

This quiz explores the concepts of cell adhesion, cell junctions, and cellular adhesion molecules in multicellular organisms. It covers the significance of stable and transient adhesive interactions and the role of junctions in maintaining tissue integrity and regulating permeability. Test your understanding of how these mechanisms contribute to cellular communication and tissue formation.

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