Cell Junctions and Adhesion Flashcards Preview

BMS 2 > Cell Junctions and Adhesion > Flashcards

Flashcards in Cell Junctions and Adhesion Deck (34):
1

Epithelial Cell structure

lateral domain connecting cell to other cells, basal domain sitting on basement membrane

2

Types of cell junctions

Tight junction

Zona

3

Tight junctions

Zona occludens

Encircle cell

Look like branches/interconnected sealing ridges in freeze fracture

Look like just tightly packed first part of cells touching in EM

4

Sealing strands

two membranes are tightly linked together by lines of transmembrane proteins
-kissing point -end of edge where two cells are touching

5

Occluding and Claudins

Mediate adhesion at tight junctions

Linked through adaptor proteins like ZO-1 to attach to actin cytoskeleton

6

Belt desomosmes

Zonula Adherens/Adeherens junction

Encircle cell and are positioned right under tight junctions

Actomyosin complex undergoes contraction to buckle epithelium to make tighter

7

Cadherins

Transmembrane proteins that mediate adhesion at belt desmosomes

Need 4 calciums to function-extracellular tail

Histdine, valine, alanine sequence facilitates formation of cadherin cis homophilic dimeres

Can also make trans dimers to attach two PMs

Cytoplasmic tail interacts with actin filaments using catenin proteins

8

Catenin proteins

3 proteins that exist in cytosol and attach cadherins to to actin-form catenins complex with actin

beta binds to caderhin and gamma, and alpha binds to actin

Beta catenin is transcriptional cofcator

9

E-cadherin

needed for tight junction formation

loss results in endothelial -mesynchemal transfoarmtion during cancer

results in cell polarity, stationarity, and cell adhesive abilities

10

Spot Desmosomes

Macula Adherens, Desmosomes

spot-like cell-cell junctions

Linked to keratin intermediate filaments achored to desmoplankin

Outer dense plaque, inner dense bplaue, dense middle line

11

Desmocollins and desmogleins

Cadherin family proteins that mediate adhesion at spot desmosomes-these are in plaques

12

Integrins

transmembrane proteins that have an α subunit and a βsubunit

Interact with ECM proteins on RGD peptide sequence

Present in actin-linked cell-matrix adhesion sites-focal adhesions

Bind ECM and internal cytoskeleton

13

alpha and beta subunit of integrin

alpha-two chains linked by disulfide linkage and globular head with binding sites for divalent cations

beta-extracellular chain with cysteine rich regions
-intracellular portion interacts with actin filaments through three connecting proteins
-talin, vinculin, and alpha actinin

14

Hemidesmosomes

Mediate interaction between cells and basement membrane
-using integrin alpha6beta4

Linked to intermediate filaments

BPG and Plectin

Consist of a plate and a plaque with keratin intermediate filaments entering PM

15

integrin alpha6beta4

Mediate interaction between cells and basement membrane

16

Focal adhesions/contacts

integrin mediated

Linked to actin cytoskeleton

Not seen without immune EM

Important for cellular processing such as migration

vinculin and talin

17

Gap junctions

Coordinate cellular rresponses

Formed by connection channels

Allow small molecules like Ca and cAMP to pass cell to cell

18

Connexin

6 connexin monomers form hexameric connexon-central open channel

Transmembrane protein

-when connexons align with connexons in adjacent cell-get hydrophilic intercellular channel

Both connections have to be open

19

Connexon permeability

Open with low Ca+, closed with high (and signals apoptosis)

also can be pH or voltage gated among other things

20

Gap junctions in pics

PM's are extremely lose together
-but can be very extensie structures (unlike tight junctions)

21

Tight junction mutation

Claudin 16

auto recessive

renal disorder

22

Belt desmosome mutation

p-cadherin

Early hair loss and progressive central retina degeneration

23

Spot desmosome mutation

Autoimmune disease with antibodies against desmoglein 1

blistering disease

cause splitting (basically empty space-vesicle)within the epidermal cell layers

24

Hemidesmosomes mutation

Autoimmune with antibodies against BPAG1 and 2-blistering disease

cause splitting (basically empty space-vesicle) between the epidermis and the underlying basement membrane

25

Gap junction mutation

Mutations in multiple different connections assocaited with deafness

26

Blistering diseases defects + facts

spot desmosomes or hemidesmosomes

-loss of adhesion of keratinocytes in superficial layers of the epidermis-pemphigus foliaceus

Antibody triggers resoponse to eosinophil chemitactic factor, the eosinophils release proteases to breadown anchoring filaments

27

Non-junctional adhesion mechanisms

Dynamic cell adhesions-found during cell locomotion where dynamic cell-cell and cell-matrix adhesions are needed

-adhesions are not always at stable junctions

also for inflammation and immune response

28

selectins

transmembrane proteins that bind oligosaccharides

Ca regualated conformation and ability to bind to carbs-binds to CRD

Expressed on surface of lymphocytes, endothelial cell, and platelets

Carbohydraterich domain (CRD)-binds to sugar

29

3 types of selectins

L-carried by lymthoctes and bind to sulfated carbs

E-expressed by activated endothelial cells

P-expressed by platelets and activated endothelial cells

30

Immunoglobulin superfamily

IgCAMs-Ig like domains on extracellular side

Ca independent

Extracellular segment of a cell adhesion molecule

Ig molecules bind either homophilically (same exact molecule) or heterophilically (any ig molecule)

31

ICAM and VCAM

play important role in the homing process

32

Leukocyte extravasation process

Leukocytes slow and and start rolling on endothelial cell surface though loose adhesion with selections binding to carbs on leukocyte cell surface

During rolling, integrins on leukocytes are activated to bind to ICAM and VCAM on endothelial cells
-Stronger interactions slow down and arrest leukocytes on cell surface

Integrin mediated migration of leukocytes through wall of blood vessel, in between the end cells

This looks like a cell is where it should not be in pictures

33

Dynamic assembly and disassembly of adhesions

Very important for cell migration

Can be intern mediated adhesions

34

Tight junctions

Belt desmosomes

Spot desmosomes

hemidesmosomes

focal adhesion

gap junctions

transmembrane protein and cytoskelton for each

occludins/claudins, actin

cadherins
actin

Cahderins (desmocollins/desmogleins) intermediate filaments

integrin alpha 6beta 4
intermediate filaments

integrins
actin

connexins
none