cell-cell junctions

beyond the cell

adhesive junctions

• adherens junction and desmosomes

adherens junctions

cell-cell adhesion

continuous zones of intermembrane attachment

20-25nm space

actin microfilaments

desmosome

cell-cell adhesion

localized points of intermembrane attachment

25-35nm space

intermediate filaments (tonofilaments)

tight junction

seals space b/w cells

membranes joined along ridges

no space

transmembrane junctional proteins, actin

gap junction

exchange of ions and molecules b/w cells

connexons (transmembrane protein complexes w 3nm pores)

2-3nm space

connexins in 1 membrane align w those in another to form channels b/w cells

cell-ECM attachments

focal adhesion and hemidesmosomes

focal adhesions

cell-ECM adhesion

localized points of attachment

20-25nm

actin microfilaments

hemidesmosome

cell-basal lamina adhesion

localized points of attachment

25-35 nm

intermediate filaments/ tonofilaments

claudins and occludins

major transmembrane protein in tight junction

claudins - proteins w 4 membrane-spanning domains

JAMs or junctional adhesion molecules

major transmembrane protein in tight junction

Immunoglobulin superfamily

lectins

• recognize and bind to specific carbohydrate (sugar) molecules on the surfaces of cells.

• They facilitate cell-cell adhesion by linking carbohydrate groups on two different cells, promoting interactions in processes like immune response, inflammation, and cell signaling.

• Animal and plant cells secrete lectins, play roles in cell recognition, adhesion, and communication.

CAMs or cell adhesion molecules

IgSF = Ig super fam

• N-CAM (neural) - 1st member

• loops like Ig in extracellular domain

• homophilic interactions

1. Selectins mediate the interaction between leukocytes and which of the following?
   
   

   • a) Platelets

   • b) Endothelial cells

   • c) Blood vessels

   • d) All of the above

D. When leukocytes interact with

platelets or the cells lining

blood vessels during

inflammation, the reactions are

mediated by selectins

1. L-selectin is expressed on

leukocytes

2. P-selectin on platelets

3. E-selectin on the endothelial

cells of blood vessels

• stable adhesions at inflammation site mediated by integrin and ICAM

Tight junctions form a continuous belt around which part of the cell?

a) Basal end

b) Apical ends of lateral surfaces

c) Entire cell surface

d) Only on one side of the cell

B. tight JUNCTIONS PREVENT THE MOVEMENTS OF MOLECULES ACROSS CELL LAYERS They form a continuous belt around the apical ends of lateral surfaces of each cell Molecules cross the cell layer by passing through the cells

The transport of ions between cells via claudins is called:

a) Paracellular transport

b) Transcellular transport

c) Active transport

d) Facilitated diffusion

A. Different tissues express different claudins

What type of movement do tight junctions block in the plasma membrane?

a) Lateral movement of lipids in the inner monolayer

b) Lateral movement of lipids in the outer monolayer

c) Vertical movement of proteins

d) Movement of water

Movement of lipids is blocked only in the outer monolayer B.

 Movement of integral membrane proteins is completely blocked

Other cell-cell adhesion events utilize other plasma membrane

glycoproteins, such as _____ and ____



IgSF proteins and selectins.

Tight junctions form a permeability barrier between epithelial cells

and prevent lateral movement of membrane proteins. They contain (1)?, (2)? and (3)?

1. occludins

2. immunoglobulin superfamily

   proteins called junctional adhesion molecules (JAMs),

3. claudins

___ junctions form open channels between cells, allowing direct

chemical and electrical communication between cells. this junction’s connexons are made of connexin proteins.

Gap