cell adhesion Flashcards
What is the primary role of cellular adhesion in multicellular organisms?
Cellular adhesion allows cells to attach to each other and the ECM, forming tissues and maintaining structural integrity
Provide examples of stable and transient cellular adhesions
Stable: Muscle-tendon connections, skin epithelial cells.
Transient: Leukocyte-endothelial interactions, cell-ECM binding during migration.
What are the main types of cell junctions?
Adherens junctions, desmosomes, tight junctions, gap junctions, and cell-matrix adhesions
What is the function of tight junctions?
They seal gaps between epithelial cells to regulate impermeability or selective permeability.
name the tight junctions
Claudin and occluding
How do gap junctions facilitate intercellular communication?
By allowing passage of small molecules and ions, enabling signal transduction
What type of adhesion do cadherins mediate?
calcium dependent homophilic adhesion
How are cadherins linked to the cytoskeleton?
through canteinins that attach to vinculin
Why are cadherin-mediated adhesions strong despite low individual affinity?
multiple cadherins interactions combine
What is a key feature of the immunoglobulin superfamily of adhesion molecules?
They mediate Ca²⁺-independent adhesion and can be homophilic or heterophilic.
What role do immunoglobulin family molecules play in immune responses?
They are critical for antigen recognition, such as T-cell receptors binding antigens.
What do selectins bind to?
Carbohydrates on glycoproteins (e.g., mucins)
How do selectins assist in immune responses?
They enable transient adhesion of leukocytes to endothelial cells, facilitating leukocyte rolling and migration.
What is the primary function of integrins?
mediate cell-ECM adhesion and signal transduction
Describe the outside-in activation pathways of integrins
Ligand binding induces conformational change, exposing cytoskeletal binding sites.
Describe the inside-out activation pathways of integrins
Intracellular signals activate integrins, increasing ligand affinity.
What specialized integrin is involved in hemidesmosome attachment?
a6B4 links epithelial cells to laminin in the basement membrane
What is the role of desmosomes?
They link intermediate filaments between adjacent cells , providing mechanical strength to tissues like the skin and heart.
name the anchoring proteins involved in desmosomes
desmoplankin
plankofilin
plankoglobin
name the cadherin family adhesion proteins used in desmosome adhesion
desmoglein
desmocollin
What is the difference between focal adhesions and podosomes?
Focal adhesions are found in many cell types, while podosomes are restricted to specialized hematopoietic cells.
How are selectins regulated during inflammation?
Inflammatory mediators (e.g., TNFα, thrombin) upregulate E-selectin and P-selectin to promote leukocyte adhesion and platelet aggregation.
What diseases are linked to defects in adhesion molecules?
Cadherin dysregulation in cancer metastasis, and integrin mutations in skin and muscle disorders.
How do integrins contribute to cell migration?
focal adhesions are dynamic and allow for cell migration
What roles do adhesion molecules play in neutrophil recruitment?
Selectins enable rolling adhesion, while integrins mediate tight binding and migration into tissues.
what are sydnecans
proteoglycans that bind proteins to ECM
