Cell Adhesion Molecules and Junctional Complexes (exam 1) Flashcards
Simple, non ciliated columnar epithelium is most likely to be found associated with which of the following
Digestive system
Junctional complexes are associated with which cellular domains
Basolateral
Transitional epithelium is associated with which system
Urinary
Although not common, stratified cuboidal epithelium may be found in which of the following areas
Part of the male urethra (also has some stratified columnar)
Lightly keratinized stratified squamous epithelium is characteristic of which of the following locations
Vaginal epithelium
What are the two components of the basal lamina
Basal lamina, Reticular lamina
What is the structure of basal lamina
Type IV collagen, Proteoglycans, Fibronectin, Laminin, Entactin
What type of collagen makes up the Reticular lamina
Type III collagen
What are the two major calcium dependent CAMs
Cadherin and Selectins
What are the two calcium independent CAMs
integrin and Immunoglobin superfamily molecules
how thick is the basement membrane
50-80nm thick
what separates an epithelial layer from its connective tissue support
Basement membrane
Does Type IV collagen form fibrils
No
Does Type I collagen form fibrils
Yes
What produces type IV collagen
Epithelial cells
What produces type I collagen
Fibroblasts
Laminin consists of how many chains
3
alpha, beta, gamma
Laminin has binding sites for what
Integrins, Type IV collagen, entactin and proteoglycans (heparan sulfate)
what is fibronectin composed of
two polypeptide chains cross-linked by disulfide bonds
What are the two forms of fibronectin
Cellular (produced by fibroblasts; part of ECM)
Plasma (secreted into bloodstream by hepatocytes)
What does fibronectin have binding sites for
Heparin (proteoglycan), Integrins, Collagen, and Fibrin
What produces the cellular form of fibronectin
Fibroblasts
What produces the Plasma form of fibronectin
Hepatocytes
what do cadherins recognize
other cadherins (same or different)
Cadherins are part of what types of junctions
Occludens and desmosomes
Selecting stabilize what types of junctions
none
integrins stabilize what types of junctions
hemidesmosomes
Selectins recognize what
Carbohydrates
Integrins bind to/recognize what
extracellular matrix molecules
Ig superfamily ligans recognize
Integrins
Ig superfamily stabilize what types of junctions
none
Classical cadherins typically form what type of dimers
cis and trans homophilic dimers
What are the there types of classical cadherins
E-cadherins (epithelial)
N-Cadherins (nerves)
P-Cadherins (placenta)
Classical cadherins are a major component in what
Calcium-mediated adherens junctions
Nonclassical cadherins include what two groups
Desmocollins and desmogleins
Where are desmocollins and desmogleins found
found in dsmosomes (macula adherens)
What are the most common types of cadherins
E-Cadherins
E-cadherins form dimers via what binding face
HVA (histidine-valine-alanine sequence)
Where is the HVA bind face of E-Cadherins found
at the tip of extracellular end of cadherin molecule
Calcium ions bind to how many extracellular domains of E-Cadherins to form cis-hemophilic dimers
4
loss of e-cadherins are associated with the invasive behavior or what
Tumor cells
what are catenins
small proteins that link the cytoplasmic end of a cadherin with cytoplasmic actin
serve as a major interface between the cadherins that hold adjacent cells together and the actin cytoskeletons of those cells.
what are the three forms of Catenins
Beta, gamma/plakoglobin, and alpha catenin
what is the function of beta and gamma/plakoglobin catenins
Attache to cytoplasmic end of a cadherin,
beta may also serve as a transcription cofactor
beta is also attached to alpha catenin
What is the function of alpha catenin
binds directly to cytoplasmic actin
how many calciums are required to bind for cadherins to funciton
4
one to each of the four domains
Which of the CAMs belongs to the lectin group
Selectins. They are carbohydrate binding
Where is the binding site for carbohydrates occurs at what location in selectins
Carbohydrate recognition domain (CRD) at the extracellular end of the selectin
Where are the calcium binding sites in selectins
Found near the CRD
Selectins are involved in the movement of what from the blood to tissues
Leukocytes
What is extravasation
The movement of leukocytes from blood to tissues by selectins
how many cellular domains do selectins have
3 extracellular domains
how many calciums must bind to a selectin
2
what are P-selectins
associated with platelets
what are E-selectins
Associated with activated endothelial cells
what are L-selectins
associated with leukocytes
What are integrins
Glycoprotens that are mainly involved in cell-extracellular matrix interactions
What do integrins bind to
EMC and cytoskeleton
integrins consist of how many subunits and what are they
two subunits
1 alpha and 1 beta
The EMC domains of interns bind to what molecules in the ECM
Fibronectin and laminin
What sequence do interns bind to
The RGD sequence in fibronectin and laminin
Laminin and fibronectin in the basement membrane interact with
collagen (including type IV), heparin sulfate proteoglycans, and entactin (nidogen)
What is interns function in hemidesmosomes
link the basal domains of cells to the ECM via the intracellular monofilaments (intermediate filaments such as keratin)
what are Immunoglobulin superfamily
Members of this family possess an extracellular segment with one or more folded domains characteristic of immunoglobulins
what are the members of the Ig-superfamily
N-CAM (neural adhesion molecules)
I-CAM-1 and I-CAM-2 ( I-CAM-1 facilitates transendothelial migration of leukocytes)
where are adherents found
on the basolateral surfaces of epithelial cells
What are adherens
molecular complexes that anchor cells together and reinforce the physical integrity of tissues and the cells that make up the tissues
What are occludens
molecular complexes that establish an impermeable barrier between adjacent cell, prevent paracellular transport and maintain concentration differences between the environments on either side of the epithelial sheets.
What are gap junctions
composed of molecular pores that enable cells to rapidly exchange ions and small molecules that help coordinate activities among the cells that make up the tissue
What is meant by Zonula
can be adherents or occludens
- travel all the way around the circumference of the cell and link all neighboring cells to the central cell.
- belt-like complexes
what is meant by macula
a macula is a “spot” or snap-like junction. often referred to as desmosomes (associated with lateral domains of epithelial cells) or hemidesmosomes (associated with basal domains of epithelial cells)
Are associated with intracellular intermediate filaments (monofilaments)
Adherens are characterized by what proteins
Cadherin (desmogleins and desmocollins)
Desmoglein 1 and 2 are found where
the epidermis
Pemphigus focialceus is caused by what
Autoantiboidies to desmoglein 1
What cadherin proteins are anchored to cytoplasmic plaques
Desmoplakin and Plakoglobin
Zonula adherens are associated with what
Actin microfilaments
Macula adherents are associated with what
intermediate filaments (tonofilaments)
What cadherins mediate interactions with filaments
Desmocollins and desmogleins
what are hemidesmosomes
anchoring junctions that anchor the basal domain of the epithelial cell to the basal lamina
what do hemidesmosomes consist of
a cytoplasmic plate associated with intermediate filaments such as keratin
a membrane plaque linking the hemidesmosome to the basal lamina via anchoring filaments (laminin 5) and interns (intern alpha6beta4)
note that at one time, hemidesmosomes were thought to be half desmosomes, with the desmosomes associated with the epithelial cells
what are the transmembrane proteins that are associated with Zonula occludens that are responsible for its tight junction
Claudins and occludins
where do occluding and claudins of zonula occludens attach intracellularly
ZO-2 and ZO-3
what is the function of JAMs and Nectin in Zonula Occludens
members of immunoglobulin superfamily. they are stabilized by disulfide bonds and form cis-homodimers that facilitate cell adhesion
nectin is associated with an intracellular molecule, afadin
JAMs are associated intracellularly with both afadin and with ZO-1
Zonula occludens proteins and afadin facilitate interaction with what type of intracellular filament
Actin
what are focal adhesions
spots that anchor the cell to the extracellular matrix via integrins
how do focal adhesions differ from desmosomes
intracellular attachment is not to monofilaments such as keratin but to actin filaments via connecting proteins
how can focal adhesions be very stable or degrade easily
the extracellular portions of the interns may be folded close to the plasma membrane and unattached to the ECM
cytosolic signals may cause the intern heads to unfold and attach to ECM components such as fibronectin or laminin
gap junctions are composed of what
connexons
how many connexins comprise a connexon
6, forming a hexagonal structure with a hollow center
Connexons facilitate movement of molecules up to what diameter
1.2nm
are connexons often clustered into patches
yes
when do gap junctions close
when the calcium ion concentrations are high
gap junctions are responsible for what
chemical and electrical coupling
What are some related pathologies to Gap junction defects
Charcot-Marie Tooth neuropathy, Congenital cataracts
do tight junctions define cell polarity
yes
are gap junctions associated with cytoskeletal components
No
basal lamina is associated with which type of collagen
Type IV
Type I collagen is associated with what
Tendons and ligaments
which of the following types of cell adhesion molecules is associated with zone occludens and desmosomes
Cadherins
desmocollins and desmoglobulins belong to what group of CAMs
Cadherins
Which of the following serve as a major interface between the cadherins that hold adjacent cells together and their actin cytoskeletons
Catenins
The extracellular domains of which of the following bind to molecules in the extracellular matrix such as fibronectin and lamina
Integrins
Which of the following are molecular complexes that anchor cells together and reinforce the physical integrity of tissues and cells that make up the tissues
zonula adherens
which of the following are molecular complexes that primarily serve to prevent parcellular transport
Zonula occludens
Which of the following is associated with the basal domains
hemidesmosomes
