Cell Interactions Flashcards
What are the three main domains of Cell adhesion molecules (CAMs)?
What are the three main families of CAMs?
The extracellular domain, the transmembrane domain and the cytoplasmic domain.
The three families are: Cadherins, immunoglobulins and selectins.
Interactions in multicellular organisms are mediated by what?
What enables interactions between cells?
Direct cell-cell contacts and indirect extracellular matrix-cell interactions.
Cell adhesion molecules enable the contacts.
What is the most prevalent CAM found in vertebrates?
What type of binding are they involved in with what other CAM molecule?
What is this binding dependent on?
What is the cytoplasmic domain linked to?
Cadherins are the most prevalent CAM. They are involved in homotypic binding with the same type of Cadherin molecule. This binding is dependent on calcium ion concentrations with high concentrations leading to binding and cell association. The cytoplasmic domain is linked to the actin cytoskeleton.
What are the characteristics of immunoglobulin-like CAMs?
Describe the PSA region of these CAMs and what they modulate.
They have immunoglobulin-like repeats and are involved in homophilic interactions with other N-CAMs. Finally these interactions are calcium ion independent.
The polysialic acid region (PSA) comprises of three carbohydrate chains with a negative charge. They modulate cell adhesion as large PSA regions repel cells and short PSA regions may bind to cells.
What do selectins/lectins bind to and what type of interaction is it?
Selectins bind weakly to olligosaccharides, these interactions being heterotypic interactions.
How are stable cellular adhesions formed?
What are the interactions between CAMs and what are the interactions between ligand-receptors?
Stable cellular adhesions are formed through clustering of multiple receptors. CAM interactions are cis interactions compared to the trans interactions of ligand-receptors.
What are the four types of cell-cell interactions?
Tight junctions,
Adherens junctions,
Desmosomes,
Gap junctions.
What are tight junctions?
These are a type of cell-cell interaction. They result in tight linkages between two membranes and the linkage between the actin cytoskeletons of both cells.
What are adherens junctions?
These are mediated by cadherins which makes the interactions calcium ion dependent. The two cells are linked by their actin cytoskeletons.
What are desmosomes?
These cell-cell interactions are associated with the intermediate filament network. Keratin filaments connect the cytoskeletons of two cells via linked desmosomes. The cell-cell membranes are linked through desmosomal proteins making the interaction indirect.
What are the three protein families involved in desmosomal linkage?
Desmosomal cadherins,
Armadillo family proteins,
Plakin family of cytolinker.
What are gap junctions?
These are formed from members of the protein connexin. These aggregate into hemi-channels which then interact to form channels 1.4nm in diameter, allowing for the selective transit of molecules.
They are found in most animal tissues such as epithelial cells and muscle cells. They can be opened and closed in response to extracellular signals.
What are the cell-cell junctions in plants called?
There are cytoplasmic links called the plasmodesmata. The ER are connected through these junctions. They allow ions and small molecules to pass through.
What is the main function of the extracellular matrix?
What are the three fundamental components of the ECM?
To provide structural and biochemical support to surrounding cells.
Collagens, glycoproteins and proteoglycans are the three main components.
What are the monomers of collagens and how are they arranged?
What are collagens characterised by?
The monomers are α-chains. Three α-chains form and triple helix.
Collagens are characterised by repetitions of specific sequences, and the conversion of prolines and lysines to hydroxyproline and hydroxylysine respectfully through post translational modification.
What are the different types of collagen aggregates?
Fibril-forming collagens, Fibril-associated collagens, 2D network-forming collagens, Filament-forming collagens, Specialised structures.
What are some diseases associated with collagen?
Mutations in fibrillar collagens can result in Ehlers-Danlos syndrome and Osteogenesis imperfecta.
Defects of collagen processing can result in scurvy which is caused by a lack of vitamin C.
What are glycoproteins?
They are diverse group of proteins which play a major role in ECM. They have a variable protein core. Attached to the peptide is a olligosaccharide. Olligosaccharides bound to serine or threonine in the peptide are called O-linked Olligosaccharides. If they are linked to asparagine they are N-linked Olligosaccharides.
What is fibronectin and what are its functions?
Fibronectin is a glycoprotein. It’s functions are to interact with multiple ECM components and it is involved in cell adhesion. It also increases the stretchability of polymers.
What are laminins?
These are a family of glycoproteins and are an integral part of the structural scaffolding in almost every tissue of an organism. They are secreted and incorporated into the ECM. They are heterotrimers, containing a α-chain, β-chain and a γ-chain. There subunits are glycoproteins and they are found in the basal lamina.
What are proteoglycans?
Like glycoproteins, they have a central protein core. They have long glycosaminoglycan side chains and N-linked oligosaccharides. They are multi domain proteins, and if they’re on the cell surface they can interact with growth factors, ECM components and CAMs.
Name four examples of tissue specific ECMs.
Basement membranes, bone, cartilage and elastic tissues.
Most cells need to be able to bind to substrates as this is essential for what cellular functions?
Stable anchoring, differentiation, proliferation, migration, signalling and survival.
The loss of cell matrix contact can cause what?
Cell death, anoikis.
