Cell adhesion Flashcards
What is the function of junctions?
Mediate cell-cell and cell-ECM adhesion
Regulate cell polarity
Involved in intercellular communication
What are the 3 main classifications of junctions?
Anchoring
Occluding
Communicating
What are anchoring junctions?
Mediate cell-cell and cell-ECM
Attachment
What are the types of anchoring junctions?
Adherens junction
Desmosome
Hemidesmosome
Focal contact
What is an adherens junctions, its location, and what is its primary protein?
Cell-cell adhesion near apical surface
Cadherin
What cytoskeletal component is associated with adherens junction?
Actin
What two anchoring junctions support each other and why?
Adherens junction and desmosomes
Resist mechanical stress and maintain tissue integrity
What is a desmosome, where is it located, and what are its main proteins?
Strong cell-cell adhesion beneath adherens junctions
Desmosomal cadherins
What are the two desmosomal cadherins?
Desmoglein
Desmocollin
What cytoskeletal component binds to desmosomes
Intermediate filaments
What are hemidesmosomes, where are they located, and what is their primary protein?
Strong adhesion between basal surface of cell and basal lamina
Integrins
What cytoskeletal component do hemidesmosomes interact with?
Intermediate filaments
What do integrins interact with in the basal lamina?
Laminin and Collagen
What are focal contacts and what is their function?
Between cell’s basal surface and ECM
Adhesion of cell to substratum
What is their primary protein and there cytoskeleton partner?
Integrins
Actin
What is the main occluding junction?
Tight junctions
What is the function of a tight junction?
Forms seal at that separates luminal/apical surfaces from intercellular space and basal surface
What are the main proteins associated with tight junctions?
Claudin
Occludin
ZO
What is the cytoskeletal partner of tight junctions?
Actin
What are the functions of tight junctions in epithelia cells?
Forms seal between adjacent epithelial cells
Regulates selective diffusion of hydrophilic molecules through paracellular space
Restricts migration of membrane proteins
Maintains cell polarity
What is the main communicating junction?
Gap junctions
What are the characteristics of a gap junction?
Hydrophilic channel formed of 2 connexons between two cells
Connexons are composed of connexin
What is the function of gap junctions?
Intercellular communication
Direct exchange of small metabolites and signaling molecules between adjacent cells
What are the four major families of cell adhesion molecules (CAMs) and what type of junction are they associated with?
Cadherin
Immunoglobulin
Integrin
Selectin
Anchoring junctions
What are the characteristics of cadherins?
Primary family
Homophilic
Cell-cell adhesion
Bind catenins that bind actin
Ca++ dependent
What are the characteristics of immunoglobulin super family of CAMs?
Homophilic and heterophilic (with self or integrins)
Mainly cell-cell
ICAM and VCAM adhesion molecules bind actin
What are the characteristics of integrins?
Cell to cell or cell-ECM
Can bind actin and intermediate filaments
What are the characteristics of selectins?
Heterophilic
Cell-cell in bloodstream
Bind carbohydrates
Bind to actin
What is the major function of selectins?
Initiating adhesion of leukocytes and platelets to endothelial cells during inflammation and hemostasis
What is the function of matrix metalloproteinases (MMPs)?
Degrade ECM
What is the function of ECM?
Structure
Shape, strength and elasticity to tissues
Substratum for adhesion
Signal transduction
Reservoir for growth factors
What is the main ECM protein family?
Collagen
What is the function of collagen?
Tensile strength and stability
What is the basement membrane?
Highly cross-linked layer of ECM that anchors epithelial cells to connective tissue
What are the functions of the basement membrane?
Compartmentalizes tissues
Physical barrier to macromolecules
Cell shape and polarity
What is laminin and what is its function?
Major component of basement membrane
Helps mediate hemidesmosomal attachment
What are glycosaminoglycans (GAGs)?
Long carbohydrate changes with anionic groups
Most are proteoglycans - linked to polypeptide core
What are types of GAGs?
Hyaluronic acid
Chondroitin sulfate
Dermatan sulfate
Keratan sulfate
Heparan sulfate
What is the function of GAGs?
Resist compressive forces
Hold H2O
What is ground substance?
Matrix of loose connective tissue made of proteoglycans
What are elastic fibers and their main components?
Form network with interwoven collagen
Elastin and fibrillin
What is the function of elastic fibers?
Allow recoil of stretched tissue, provide elacticity
What is fibronectin?
Adhesion glycoprotein that attaches cells to other ECM components via integrins
What is fibrinogen?
Protein component of blood clots that can connect with integrins and fibronectin
How is fibrin made?
Cleavage of fibrinogen by thrombin
