Cell-Cell interactions Flashcards
Name the 4 main categories of signalling and any sub-categories that are included
- Cytoplasmic connections between cells
- Cell-to-cell signals
- Cell-matrix
- Free diffusion of chemical signals between cells
- Adjacent cells (paracrine/ synaptic)
- Distant cells (endocrine)
Whats a juxtacrine signal?
Cell-to-cell contacts at the plasma membrane
Tell me about juxtacrine signals
- Have to have physical contact between cells
- signalling occurs at all cell-cell contact centres
In cell-cell contact, what happens at speciaised regions on the membrane and at non-specialised regions on the membrane ?
Specialised regions on the membrane
- Signalling and tissue organisation and behaviour
Non-specialised regions on the membrane
- Signalling and movement/ migration
What can cells have specialised regions for?
Cell-cell signals (desmosomes-tight junctions etc) in some cases
Name the cell adhesion molecules
Label which are the specialised contact cells
Label which are the non-specialised contact cells
Label which experience Homophilic interactions
Label which experience heterophilic interactions
What are the subtypes of cell-cell specialised junctions and their sub-sub types
1. cell-cell contacts at organised junctions
- tight junctions (vertebrates)
- Septate junctions (invertebrates)
2. Anchoring junctions
- Adherence junctions-adhering protein’s present (actin attachment sites)
- Desmosomes (intermediate filament attachment sites e.g. Keratin)
3. Communicating junctions
- Gap junctions
- Electrical synapses
Label the junctions of the epithelial cell
Whats a Functional syncytia?
Fused cells with multiple nuclei with intercellular cytoplasmic connections
What size molecules can diffuse through the limited size cytoplasmic pores ?
<1000 Da
What does the plasmodesmata between cells allow?
Electrical coupling from one cell to the other
The cell-cell gap junctions are made of what?
Homo and heteromeric made of connexin 4 pass proteins- 14 family members present either in singla gap junctions or in groups of thousands (e.g. cardiac intercalated discs)
Is the pores in cell-cell gap junctions regulatable ?
yes
What are the different types of connecting forms in cell-cell gap junctions ?
Can gap junctions be concentrated together?
yes
Tell me about the regulation of gap junctions?
The channels close at high Ca2+ concentrations and low pH, allowing regulation of the coupling of cells (stops apoptosis of one cell affecting those connected via gap junctions)
is phosphorylation reversable and regulated?
yes
Where does histidine and aspartate phosphorylation occur?
In plants and prokaryotes
What does phosphorylation cause a conformational change in?
Many enzymes and receptors causing activation or deactivation
What does the addition of a phosphate to a weakly polar R group such as serine/ threonine cause?
Turns a hydrophobic region into a hydrophilic/ charged region
what does conformational change allow?
substrate binding to occur at these regions
What two things can happen in cell signalling ?
- Either a cell surface receptor is a kinase which is activated by binding to its ligand
- A signal at the cell surface causes transmembrane proteins to cluster and bring binding parterns including kinase and their substrates together
What are kinase receptors activated by?
binding its ligand, dimerisation and autophosphorylation
what do kinase receptors produce?
An amplifying signalling cascade
