Module 8 review (cells and tissues)

What are the major types of cell adhesion receptor proteins? (theres 4)

• immunoglobulin (IgCAMs)

• Cadherins

• Integrins

• Selectins

What are the major type of intracellular junctions (theres 5)

• tight junctions

• gap junctions

• Adheren junctions

• Desmesomes

• Focal adhesions/hemidesmosomes

what is the purpose of cellular adhesions?

to interact with their envionment

What are the types of cellular adhesions and where are you likely to see them?

permanent: along muscle or skin cells to adhere firmly to each other

transient/dynamic: at sites of inflammation for lekocytes to migrate past endothelial cells

What are the 4 major cell adhesion proteins?

immunoglobulins (IgCAM)

Cadherins

Integrins

Selectin

What are the domains of IgCAMs?

•Ig domains and fibronectin domains

how do IgCAMs bind?

Homophilically

They bind with other IgCAMs on other cells and with integrins

Q: Is IgCAM-mediated cell adhesion transient or permanent?

A: Transient.

What are NCAMs and what do they do?

Neural cell adhesion molecules

•Helps neurons grow and form connections

What are VCAM-1s and what do they do?

Vascular Cell Adhesion Molecule

•Found on blood vessel walls during inflammation

What are ICAMs and what do they do?

intercellular adhesion molecules

•Assists leukocytes in moving to areas of infection

What is seen in the image of the desmosome and adheren junction?

What is the domain for Cadherins?

CAD

What do cadherins depend on for their rigid shape

calcium

How do cadherins bind?

mostly homophilically between cells at specialized junctions called adheren junctions or desmosomes (cytoplasmic side links to actin filaments or intermediate filaments)

Where are E-cadherins found

epithelial cells

where are N-cadherins found?

nerve and muscle tissues

Where are desmogleins (a type of cadherin) found?

desmosomes of the epithelim and heart

Q: What is the major function of integrins?

A: Responsible for anchoring the cell to the ECM with the actin cysoskel

Q: What are the extracellular ligands of integrins?

A: Fibronectin and laminin.

Q: What happens during focal adhesions?

A: Integrins cluster together and link to actin filaments.

Integrins transducer signals related to?

What does loss of contact result in?

cell adhesion, locomotion and differeentiation

apoptosis

Integrins are ______ composed of two different transmembrane polypeptides:

• ?

• ?

heterodimers

• Alpha (α) chain

• Beta (β) chain

which ECM ligands can integrins bind?

• Fibronectin

• Laminin

How do integrins link the ECM to the cytoskeleton

Integrins bind ECM proteins (fibronectin and laminin) and connect the ECM to the actin cytoskeleton inside the cell.

how do integrins participate in signaling?

they transduce signals related to cellular adhesion, locomotion, and differentiation.

how do integrins participate in migration?

Integrins cluster together at focal adhesions, which are highly dynamic and rapidly assembled and disassembled to allow cell migration

how do integrins participate in differentiation?

Integrins transmit signals involved in cellular differentiation.

Selectins are _____-dependendent

calcium

what is domain of selectins?

lectin (calcium dependent)

Q: What are the ligands of selectins?

A: Mucin glycoproteins.

Q: What is the function of selectins?

A: Snare circulating white blood cells and platelets.

Q: Where is L-selectin found?

A: On the surface of white blood cells.

Q: Where is P-selectin found?

A: On platelets and endothelial cells.

Q: Where is E-selectin produced?

A: By endothelial cells during inflammation.

Q: What are the three cell adhesion receptors that attach cell to cell?

A: IgCAMs, cadherins, and selectins.

Q: What junctions are associated with cadherins?

A: Adherens junctions and desmosomes.

Q: What cytoskeletal filaments do cadherins connect to?

A: Actin or intermediate filaments.

Q: What do selectins bind to?

A: Glycoproteins.

Q: Is selectin-mediated adhesion transient or permanent?

A: Transient.

Q: Which cell adhesion receptor attaches cells to the ECM?

A: Integrins.

Q: What ECM components do integrins bind to?

A: Fibronectin and laminin.

Q: What junctions are associated with integrins?

A: Focal adhesions and hemidesmosomes.

Q: What cytoskeletal structure do integrins connect to?

A: Actin cytoskeleton.

What is the following cell adhesion protein?

What is the following cell adhesion protein?

integrin

What is the following cell adhesion protein?

selectin

What is the following cell adhesion protein?

IgCAM

How do selectins recognize their ligands

Selectins have a calcium-dependent lectin domain that binds to oligosaccharides on mucin glycoproteins.

With selectins, why are rapidly reversible bonds useful?

Allows them to temporarily capture circulating white blood cells and platelets.

What are the steps of leukocyte extravasation?

Rolling → Activation → Tight binding (firm adhesion) → Diapedesis and Migration

give the adhesion proteins for leukocyte extrasation

______ → rolling

______ → Integrin activation

______ → Firm adhesion

______ → Diapedisis

______ (not a protein) → tissue migration

Selectins → rolling

Chemokines → Integrin activation

Integrins + ICAM-1 → Firm adhesion

PECAM-1 → Diapedisis

Chemotaxis → tissue migration

the temporary interactions (due to rapid reversal) allow leukocytes to make loose connections with endothelial cells during ?

leukocyte rolling.

•___-selectin and ___-selectin on endothelial cells bind sialyl Lewis X glycoproteins on leukocyte causing?

P; E

Loose transeint adhesion

during integrin activation of leukocyte extrasation, ______ shift lekocyte integrins to a _____-affinity state

chemokines; high

in leukocyte extrasation, ________ directs movement (tissue migration) to the site of infection or injury

chemotaxis

what are the 6 types of cellular junctions?

tight junction

Gap junction

Adheren junctions

Desmosomes

Focal adhesion

Hemidesmosomes

which of the 6 cell junctions link cell-cell (cells together)

tight, gap, adherens, and desmosomes

which of the 6 cell junctions link cell-ECM

Focal and hemidesmocomes

WHat are tight junctions

intracellular connection that connects two plasma membranes of two cells together sealing the extracellular space and limiting diffusion of ions and solutes between cells

______ Allows cells to create different extracellular environments on the two sides of the epithelium

Tight Junctions

what are tight junctions linked to?

actin of the cytoskeleton

what are tight junctions made of?

Claudin and occludin

How are tight junctions organized?

form the zonula occludens which encircle cells near their apical surface.

they form belt-like connections between the plasma membranes of adjacent cells

what are gap junctions?

intracellular connection channels between the cytoplasm of adjacent cells that allow small molecules to pass to neighboring cells (coordinate activity between adjacent cells)

what can pass through gap junctions?

small molecules like water, ions (Ex. Ca2+), second messengers (Ex. cAMP) and metabolites

Larger molecules like proteins

What are gap junctions made of?

hexagonal ring of connexins

How are gap junction channels assembled from connexin?

form channels that connect the cytoplasm of adjacent cells and make a continious pore that exist in plaques

What are adherens?

intracellular connection that link neighboring cells, maintain integrity of the cell, transmit mechanincal forces between cells and establish polarity

what do adherens connect to?

actin filamints

what are adherens composed of?

cadherins

Adherens junctions (Also called zonula adherens) link neighboring cells together and encircle cells near their _____ surface.

apical

in Adherens, the connections to actin filaments allow _______ to be transmitted between cells.

mechanical forces

What are demosomes?

intracellular connection that links adjacent cells and function to provide support and allow for cell signaling

What do desmosomes link to?

intermediate filamins (keratin)

what are desmesomes made of?

Cadherins (desmoglein)

How does pemphigus vulgaris interfere with desmosomal adhesion?

autoantibodies interfere with desmosomal adhesion, weakening the connections between adjacent cells resulting in blistering

What are focal adhesions?

transient/dynamic (rapidly assembled/dissambled) intracellular connection that allows for cell migration and mechanosensing/signaling

What do focal adhesions link to?

acin

what are focal adhesions made of?

integrins

What are hemidesmesomes?

intracellular connection is stable and long lasting and functions to allow long-term anchoring and withstand mechanical sheer

What do hemidesmosomes link to?

Intermediate filaments (keratin)

What are hemidesmosomes made of?

integrins

what do hemidesmosomes llink to?

laminin

How is bullous pemphigoid associated with hemidesmosomal defects?

autoantibodies disrupt hemidesmosomal adhesion, weakening the attachment of epithelial cells to the basal lamina.

_______ help maintain selective permeability

Intercellular junctions

_______ and _______ form lateral connections between cells

•Desmosomes and gap junctions:

_________ anchor cell to basal lamina

Hemidesmosomes

What is the type of intercellular junction pictured?

tight junctions

(notice the belt like appearance)

What is the type of intercellular junction pictured?

tigh junctions

What is the type of intercellular junction pictured?

Gap junctions

(notice the large amounts of hexagonal rings)

What is the type of intercellular junction pictured?

gap junctions

What is the type of intercellular junction pictured?

adherens

(kinda looks like a desmosome but with no dark ring)

What is the type of intercellular junction pictured?

Desmosomes

(notice the dark ring)

What is the type of intercellular junction pictured?

Desmesomes

(notice the dark ring)

What is the type of intercellular junction pictured?

Focal adhesion

What is the type of intercellular junction pictured?

hemidesmosomes

(notice how its only half of a dark spot and its connected to a membrane not another cell)

A cell must adhere tightly to a neighboring epithelial cell through a calcium-dependent receptor. Which receptor family is most likely involved?

A. Selectins

B. Cadherins

C. Integrins

D. Connexins

B. Cadherins

A migrating cell needs to attach to fibronectin and connect that contact to actin. Which receptor is most directly responsible?

A. Integrin

B. Claudin

C. Desmoglein

D. Connexin

A. Integrin

During inflammation, a leukocyte initially rolls along the endothelium. Which interaction mediates this step?

A. Connexin with connexin

B. Desmoglein with keratin

C. Endothelial selectin with sialyl Lewis X

D. Laminin with collagen IV

C. Endothelial selectin with sialyl Lewis X