Desmosomes: Structure, Function, and Importance in Cell Adhesion

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Questions and Answers

Quel rôle les desmosomes jouent-ils dans la stabilité mécanique des tissus?

Ils influencent l'expression génique et la survie cellulaire.

Ils scellent l'espace extracellulaire entre les cellules connectées.

Ils résistent aux forces externes en connectant les cytosquelettes des cellules voisines. (correct)

Ils permettent le passage direct de petites molécules entre les cellules adjacentes.

Comment les jonctions serrées se distinguent-elles des desmosomes?

Elles permettent le passage direct de petites molécules entre les cellules adjacentes.

Elles résistent aux forces externes en connectant les cytosquelettes des cellules voisines.

Elles scellent l'espace extracellulaire entre les cellules connectées. (correct)

Elles facilitent l'adhérence cellulaire via des cadhérines, mais sans attache aux filaments intermédiaires.

Quelle fonction ne partagent pas les jonctions adherens avec les desmosomes?

Connection aux filaments intermédiaires.

Communication indirecte avec le cytosquelette.

Passage direct de petites molécules entre les cellules. (correct)

Adhérence cellulaire via des cadhérines.

Pourquoi les desmosomes sont-ils importants dans la formation de barrières protectrices?

Ils aident à maintenir une barrière protectrice contre les irritants et les pathogènes. Signup and view all the answers

Que partagent en commun les jonctions serrées, les jonctions adherens et les desmosomes?

L'adhérence cellulaire via cadhérines. Signup and view all the answers

Comment les composants des desmosomes modulent-ils les voies de signalisation cellulaire?

En influençant la prolifération, la différenciation et l'apoptose. Signup and view all the answers

Quel est le rôle principal des desmosomes?

Assurer la cohésion et la résistance au stress mécanique entre les cellules épithéliales. Signup and view all the answers

Quels sont les composants principaux des desmosomes?

Des cadhérines et des protéines cytoplasmiques de plaque. Signup and view all the answers

Comment les cadhérines contribuent-elles à l'attachement intercellulaire des desmosomes?

Elles forment des homodimères sur les membranes cellulaires adjacentes. Signup and view all the answers

Quelle est l'importance de l'association des desmoplakines avec les filaments d'actine pour les desmosomes?

Renforcer la structure mécanique et permettre la communication avec le cytosquelette. Signup and view all the answers

Comment les desmosomes se distinguent-ils des autres jonctions cellulaires?

Ils permettent une forte adhérence intercellulaire indépendamment de la concentration de calcium extracellulaire. Signup and view all the answers

Pourquoi les desmosomes sont-ils particulièrement importants dans les régions anatomiques exposées au mouvement, comme le cœur?

Pour contribuer à la résistance du tissu contre les forces de cisaillement. Signup and view all the answers

Study Notes

Desmosomes

Desmosomes are specialized intercellular junctions found primarily between epithelial cells. These structures play a crucial role in maintaining tissue integrity and ensuring proper cell behavior within tissues such as skin, hair follicles, cornea, and cardiac muscle. Here's what you need to know about their structure, functions, distinctions from other cell junctions, and relevance to cell adhesion.

Structure of Desmosomes

Desmosomes consist of two main components: transmembrane proteins called cadherins and cytoplasmic plaque proteins such as plakoglobin and plakophilins. Cadherins form homodimers on adjacent cell membranes, enabling strong intercellular attachment through hydrophilic interactions independent of extracellular calcium concentration. On the intracellular side, desmoplakins are associated with actin filaments, providing mechanical strength and allowing communication with the cytoskeleton. This connectivity contributes to tissue resistance against shear forces, which is particularly important in anatomical regions exposed to movement, like the heart.

Function of Desmosomes

The primary function of desmosomes is to facilitate strong adhesive contacts among various types of polarized epithelial cells and strengthen the connections between them. They ensure cohesiveness and resistance to mechanical stress, which is essential for maintaining structural and functional integrity of tissues. Furthermore, desmosomal components also modulate cell signaling pathways involved in proliferation, differentiation, and apoptosis (programmed cell death).

Distinguishing Desmosomes from Other Cell Junctions

While similarities exist across all cell junction types regarding protein composition and function, there are distinct differences:

Tight junctions: These seal off extracellular space between connected cells.
Gap junctions: These allow direct passage of small molecules (less than 1 kDa) between adjacent cells.
Adherens junctions: Like desmosomes, these facilitate cell–cell adhesion via cadherins; however, they lack intermediate filament attachments and communicate indirectly with the cytoskeleton.

Each type of junction plays specific roles in regulating cell behavior and maintaining organismal homeostasis.

Importance of Desmosomes in Cell Adhesion

Cell adhesion refers to the interaction between cells, mediated by various ligands and receptors present on the cell surface. In this context, desmosomes serve several critical purposes:

Mechanical stability: By connecting the cytoskeletons of neighboring cells, desmosomes contribute to overall tissue rigidity and resist external forces.
Regulation of gene expression: Desmosomes can influence cell division, growth, and survival, especially during development when cells undergo rapid changes in shape and size.
Protective barrier formation: In certain tissues like the epidermis, desmosome-mediated cell adhesion helps maintain a protective barrier against irritants and pathogen invasion.

In summary, desmosomes represent a complex interface where cells meet, interact, and exchange information vital for the maintenance of multicellular life. Their structure, function, distinction from other cell junctions, and importance in cell adhesion collectively underscore their significance in biology.

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Description

Explore the structure, function, and significance of desmosomes in cell adhesion, focusing on their role in maintaining tissue integrity and facilitating strong adhesive contacts among epithelial cells. Learn about how desmosomes differ from other cell junctions and their impact on cell behavior and tissue resistance against external forces.