cell junctions, adhesion molecules, and extracellular matrix Flashcards
What two major groups to CAMs (cell adhesion molecules fall under)
Calcium dependent
- Cadherin
- selectins
Calcium independent
- Integrins
- Immunoglobulin super familiy molecules
What are cadherins?
classical
- Calcium mediated adheren junctions
- form cis and trans homophillic dimers
- occurs at N terminal tips
- E-cad = epithelial
- N- cad = nerve
- P cad = palcenta and epidermis
Nonclassical
- Include desmocollins and desmogleins
- dound in desmosomes
What is the cadherin superfamily?
Cadherin binding motif
on the extracellular side of cadherins binds to the N terminal of the adjacent cadherin
Calcium present at hinges between Ca2+ ions bind to sites near hinge to prevent it from flexing. removal of Ca2+ causes flexing at hinges
because instracellular portions are varied they are able to affect the way cadherins anchor to cytoskeleton
what are thec haracteristics of cadherin-mediated adhesion?
cad binds to each other with low afffinty.
Strength comes from many clusted parrallel bonds b/w N terminals and tail and anchor proteins
stogng and easily dissaembled charcteristics works well with actin treadmilling
What selective recongition via cadherin?
mediates highly selective recognition enabling cells of similiar type to stick together and stay segregated from tighter cells (sorting out)
b/c homophillic binding
Low yield test questions below
altering of properties causes formation of neural crest. cells then migrate away and form different cell types and tissues throughout embryo
Neural tubes leaves ecto derms and forms losing E cad and expressing N cad. Then Cad 7 appears that helpsmigrats cells . When cells aggregate to form ganglion it reexpresses N Cad
What is E cadherins?
- Most common type of cadherins
- form Dimers via HVA binding fact
- found at tip of CAD molecule
- Ca 2+ bind to four EC domains and dacilitate Cis homphilic dimers
- loss of E cad assoc w/ tumor invasions
What is catenins?
Small proteins that link the cytopalsmic end of cadherin with cytoplasmic actin. They serve as a major interact b/w cadherins that hold adjacent cells together and the actin cytoskeletons of those cells
Beta and y/plakoglobin (not y its greek) catenins
- attached to cytopalsmic end of cadherin
- beta may also serve as transcription cofactor
- beta is also atached to alpha catenin
Alpha catenin
- binds directly to cytoplasmic end of actin
What is selectins?
Binds to carobohydrates is located at the CRD at EC end of selectin
CA2+ fights also found near CRD and Calcium is required for binding activity
Involved in movement of leukocytes from blood to tissues (extravasation)
P - selectins = platelets
E - sel = endothelial
L -sel = leukocytes
What are integrins?
are glycoproteins that mainly involved in cell-extracellular matrix interactions
ECM binds to fibronectin and laminin (their RGD seq)
1 alpha and beta subunit
Hemidesmosome interact with collagen IV, heparan sulfate proteioglycans, and enactin and link basal domains of cells to ECM matrix with intracellular tonofilaments (intermediate filaments like
What is the immunoglobulin superfamily?
Possess an extracellular segment with one or more folded domains characteristics of immunoglobulins
Members of IG superfamily
N-CAM = neural ; mediate homo/hetero phillic interactions
I CAM1 and ICAM2 facilitates transendothelial migration of leukocytes
What are adherens
adheres and is basal lateral surfaces
includes zonula and macula
- assocated by interaction with cadherins
- desmocollins and desmogleins
What are occludens?
establish an imperable barrier b.w adjacent cells that prevents paracellular transport and maintains concentration gradient
Lateral side
What are gap junctions?
Pores that composed of molecular pores that enable cells to rapidly exchange ions and small molecules that coordinate activatie among the cells that make up tissue
What is zonula?
adherens or occuldens
travel all the way around the circumference and belt like complexes. assoc w. intracellular actin
What is a macula?
Macula
a macula is a spot or snap like junctions ; adheren only. assocated intermediate filaments ( tonofilaments
Desmosomes associated lateral domains
Hemidesmosomes associated basal domain
What is a hemidesmosome?
anchoring junctions that anchor the basal domain of the epithelial cell to basal lamina
cytoplasmic plate associated with intermediate filaments such as keratin
membrane plaque linking the hemidesmosome to basal lamina via anchoring filaments (laminin 5) and integrinsALpha 6 beta 4)
