Cell - Cell Recognition and Adhesion Flashcards
in order to associate in precise patterns, cells must..?
cells must recognize, adhere to, and communicate with each other
how do transmembrane proteins mediate cell-cell adhesion?
many of the adhesion proteins are transmembrane proteins, which means?
adhesion proteins are continuously….?
- use specialized adhesion receptors to attach to one another
- many of these adhesion proteins are transmembrane proteins, which means the extracellular portion of these proteins can interact with the extracellular portion of similar proteins on the surface of neighboring cells
- continuously recycled
What are the classes of cell-cell adhesion receptors? (4)
- Immunoglobulin superfamily (IgSF)
- cadherins
- selectins
- integrins
kinds of interactions of cell-cell adhesion receptors? (2)
- Homophilic interactions
2. Heterophilic interactions
interactions of cell-cell receptors:
How do homophilic interactions work?
what classes of cell-cell adhesion receptors fall under this category?
- cells with identical receptors on their surfaces interact with one another
- cadherins and IgSF
Interaction of cell-cell receptors:
How do heterophilic interactions work?
What classes of cell-cell adhesion receptors fall under this category?
- cells with different recptors interact
- selectins and intergrins
many adhesion receptors also interact with?
the cytoskeleton via linker proteins
Immunoglobulin super family (IgSF):
- members of the IgSF?
- first known member of the IgSF family?
- structure of proteins in this family?
- how do homophilic interaction occur?
- cell adhesion molecules (CAMS) are members of the IgSF
- the first known member of the family is a neural cell adhesion molecule, N-CAM, identified using an antibody that disrupted cell-cell adhesion between isolated neural cells
- proteins in this family have well organized loops in extracellular domains: homophilic interactions occure via these domains
Cadherins:
- what are they? where are they found?
- what is their role?
- how can CAM’s and cadherins be distinguished from each other?
- structure of cadherins?
- important group of adhesive glycoproteins, found in the plasma membrane of most animal cells
- play a crucial role in cell-cell adhesion and recognition (similar to CAMS), roles in embryonic development, help neuronal cells form bundles
- cadherins require calcium for binding, but CAMS do not
- cadherins have a series of similar domains (repeats) in their extracellular domains
different type of cadherins are expressed in..? why?
particular tissues - the amount and type of cadherins on cell surfaces help segregate cells into particular tissues
what cadherin is the best characterized cadherin?
structure? how does the structure help?
where can you find them?
- E-cadherins are best characterized cadherin
- five repeats on its extracellular domain through which two E-cadherin molecules can interact by “zipping together”
- found on epithelial cells in pairs on the plasma membrane; their cytosolic portions interact with the cytoskeleton
What is the epithelial mesenchymal transition (EMT)
the breakdown of epithelium into loosely organized mesenchyme cells, is accompanied by changes in the cadherin expression
Selectins and Leukocyte Adhesions:
what is the relationship between selectins and leukocytes?
Where are the different types of selectins expressed?
Stable adhesions at the site of the inflammation are mediated by..?
- leukocytes function/interaction with platelets or cell-lining blood vessels is mediated by selectins
- L-selectin is expressed on leukocytes, P-selectin on platelets, E-selectin on the endothelial cells of blood vessels
- Stable adhesions at the site of inflammation are mediated by an integrin and ICAM
what happens to leukocytes when inflammation occurs?
leukocytes attach to the wall of a blood vessel in the vicinity of the imflammation and then migrate through the blood vessel to the inflammation site. The initial attachment of leukocytes is mediated by binding of selectins on the leukocyte to the carbohydrates on the surface of the endothelial cells, and vise versa. When leukocytes start rolling and begin to invade the blood vessel, they make more stable adhesions, which are mediated by a specific integrin on the surface of the leukocyte and IgSF proteins called ICAMs, on the surface of the endothelial cells
What affects the adhesion properties of CAMs and cadherins?
The carbohydrate side chains
the carbohydrate side chains of CAMs and caderins affect their adhesion properties:
Lectins
-what are they?
-what do they do?
-how many cells can they bind to carbohydrate groups? what does this do?
- secreted carbohydrate-binding proteins
- promote cell-cell adhesion by binding a specific sugar or sugars at the outer cell surface.
- b/c lectins usually have more than one carbohydrate binding site, they can bind to carbohydrate groups on two different cells. thereby linking the cells together
Carbohydrates and the survival of erythrocytes:
What is one well known example of the importance of carbohydrates at the cell surface?
the determination of of the human blood types, A,B, AB, and O by a specific carbohydrate
Carbohydrates and the survival of erythrocytes:
How can you differentiate between blood type A,B,AB,and O?
-ABO blood group involves differences in carbohydrate attached to a glycolipid on the surface of red blood cells
Carbohydrates and the survival of erythrocytes:
Determination of blood type A
the amino sugar N-acetylglycosamine is found at the end of the carbohydrate
Carbohydrates and the survival of erythrocytes:
Determination of blood type B
the sugar galactose is at the end of the carbohydrate
Carbohydrates and the survival of erythrocytes:
Determination of blood type AB
both sugars (N-acetylglycosamine and galactose) are present
Carbohydrates and the survival of erythrocytes:
Determination of blood type O
neither sugar (N-acetylglycosamine or galactose) is present
