BIO 211 Lecture 13 Cell Junctions and Matrix

forces

Morphological changes in the tissue are caused by — from within the tissue

convergent extension

a tissue or structure extends in one direction while narrowing in the perpendicular direction

cell division, size

after the egg is fertilized, multiple rounds of — occurs

• embryo does not change —

primitive gut

gastrulation results in formation of the —

Blastulation

the stage of embryonic development that follows cleavage and results in the formation of a hollow ball of cells

• Establishes the first major differentiation between cells, leading to specialized structures.

gastrulation

a crucial phase in embryonic development where the single-layered blastula is reorganized into a three-layered structure. This process establishes the three primary germ layers:

1. Ectoderm

2. Mesoderm

3. Endoderm

cadherins

calcium-dependent adhesion proteins that mediate cell-cell adhesion in tissues

• transmembrane receptors

transmembrane

cadherins are — receptors

extracellular

the — side of cadherins binds to other cadherins

intracellular

the — side of cadherins binds to catenins, which link cadherins to the actin cytoskeleton

each other

Desmosomes link cells to —

basement membrane

Hemidesmosomes link cells to the —

intermediate

Desmosomes/hemidesmosomes plug into — filaments

• Provide structural strength

• Desmosomes do not have as much of a role in generating force

tight junctions

seals gap between epithelial cells

• composed of a network of proteins that create a barrier

• Connect the cells so tightly that not even ions can flow past this connection!

adherens junction

connects actin filament bundle in one cell to actin filament bundle in the next cell

desmosomes

connects intermediate filaments in one cell to intermediate filaments in the next cell

gap junctions

allow direct communication between adjacent cells

• they enable the transfer of ions, small molecules, and electrical signals

hemidesmosome

anchors intermediate filaments in a cell to the ECM

actin linked cell matrix junction (focal adhesions)

anchors actin filaments in cell to ECM

• vinculin

calcium

— is required in the extracellular space for the homophilic binding to occur

other cadherins

Ligand that cadherins bind are —

homophilic, identical

Cadherins form — connections with other cells that have — cadherins

N-terminal

Only the very — domains of cadherins interact

hinge regions

calcium binds to cadherins at —

rigid

calcium makes the overall protein more —

cadherins

the core component of adherens junctions is —

P120-catenin

— helps the cadherin get expressed at the plasma membrane

B-catenin

— helps connect a-catenin to cadherin (adaptor)

a-catenin

— provides bridge from cadherin receptor to actomyosin filaments

a-catenin

— stretches in response to force, revealing a new vinculin binding site, allowing more actomyosin filaments to be recruited and more force to be applied

proteoglycan

composed of a core protein covalently linked to one or more glycosaminoglycan (GAG) chains

GAGs

long, unbranched polysaccharides composed of repeating disaccharide units

highly charged

sugar

Proteoglycans are more — than protein

type 1 collagen

component of loose, reticular stromal matrix

type 4 collagen and laminin

components of basement membrane

triple helix

a collagen fiber is a — (structure)

dimer

fibronectin is a — (structure)

protein

glycoproteins are nearly all —

Aggrecan, shock absorber

— is enriched in cartilage where is acts like a — to protect the joints from mechanical stress due to its high degree of hydration

fibronectin

Collagen helices can be bundled together by covalent cross linking by accessory proteins like —

organize

Fibronectin and other multidomain glycoproteins help to — the matrix

binding domains

Each fibronectin dimer contains multiple —

fibronectin, type 1 collagen

• When a blood vessel is severed, — spills out into surrounding stroma

  • Stroma enriched in —

  • Fibronectin binds collagen and binds to any nearby cells, providing them with additional adhesive sites to move along the fibronectin bound collagen

tension, adhesive sites

when — is applied to fibronectin, it unfolds and exposes new — for protein-protein interactions

force

Cells in the stroma are not fully capable of binding until cell applies — to fibronectin

focal adhesions

Fibronectin concentrated at ends of — of stress fibers

• allows force to be transmitted to fibronectin when it is outside the cell

Integrin

— applied forces are critical to unfold and activate fibronectin, allowing for further binding of collagen

integrins, cadherins

Focal adhesions use —

Adherens junctions use —

focal adhesions (actin linked cell-matrix junction)

talin, vinculin, integrin (components of —)

adherens junctions

a-catenin, vinculin, cadherins (components of —)

type 4 collagen and laminin

components of basal lamina

Hemidesmosomes

How to attach cells to basal lamina:

1. Focal adhesion

2. —

Focal adhesions

How to attach cells to basal lamina:

1. —

2. Hemidesmosomes

fibronectin

— acts as a signal during development/wound healing

• Tells the tissue that we need more cells/adhesion in an area

actomyosin contractility

Tissue shaping = spatially and temporally regulated — and adhesion in epithelial cell monolayers

Marfan syndrome

mutation in the matrix protein fibrillin-1

• matrix in the iris is weak

• If they bang their head, the lens can shift from the iris

Iris

— = heavily rich in matrix

• Fibers oriented towards the lens

• Fibers hold the lens in place at the center of the eye so the lens can properly focus light onto the retina

ECM

— provides signals telling cells where to go, what to do, etc

• ghost hearts

GAGs, water

— are too stiff to be tightly folded, so these very long, negatively charged molecules attract a lot of — to shield the charges

hydrated gels

GAGs occupy large amounts of space and form —

hyaluronan

— is a large GAG that is produced at the cell surface by a complex of enzymes

• important in development and wound healing by providing a transient space-filling material that can maintain the shape of a tissue while cells migrate

maintain the shape

Hyaluronan, a large GAG, is important in development and wound healing by providing a transient space-filling material that can — of a tissue while cells migrate

hyaluronidase

Excess hyaluronan is degraded by —

outside

Proteoglycans are produced — the cell

• The protein component of proteoglycan is produced in the cell and secreted, and then docked and GAG-creating enzymes are recruited to create the proteoglycan

connections, flat

Laminin and type 4 collagen form many —, so they are able to form a barrier

• makes the basement membrane —

glycoprotein

fibronectin is a — (proteoglycan/glycoprotein)

glycoproteins

— are found in basement membranes

proteins that have carbohydrate chains covalently attached to their polypeptide chains

• Ex. Fibronectin

proteoglycan

a special type of glycoprotein characterized by their extensive carbohydrate content, specifically glycosaminoglycan (GAG) chains. These molecules are essential components of the extracellular matrix and play vital roles in cell signaling and structural support

• excellent shock absorber

proteoglycan

aggrecan is a —

glycoprotein

laminin is a —

glycoprotein

fibronectin is a —

disaccharides

GAGs are made of repeating —

ER

The core protein of proteoglycans is produced in the —

Golgi

Polysaccharides are added to the protein in the — to make the proteoglycan