Cell-to-Cell Contact and Extracellular Environment

Evolution Ecology And Organismal Biology 415 with Bronson at Ohio State University - All Campuses

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By: Hannah Novinc
Created: 2012-02-14
Size: 35 flashcards
Views: 13

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Cell Attachments Function

Maintain cohesion of metazoan

Provide structure and support

Facilitate communication

Allow for migration

Functional Classes of Junctions (Jxns)

Anchoring: tether, strength

-Cell-to-cell: Adherens (AF) or Desmosomes (IF)

-Cell-to-matrix: Adhesions (AF) or Hemidesmosomes (IF)

Occluding: seal gaps between cells = tight jxns in vertebrates; septate jxn in invertebrates

Channel-forming: connect cytosols = gap jxns

Signal-relaying: transfer information = synapsis

CTC Cadherins

Mediate cell

Ca 2+ - dependent

-extends dimer

-allows homophilic binding

Tissue specific

In all Animals, almost all cells

Critical role in development

-Organize similar cells

-Expression changes during development

CTC Adherens Junctions

Cadherins linked to cytoskeletal AFs

Hold cell together

Often form adhesion belts

In epithelial and non-epithelial tissues

Contraction of anchored Afs causes folding of tissue layer

CTC Desmosomes Junctions

Cadherins linked cytoskeletal IFs

Hold cell together

Mechanical Strength

Examples:

-Epithelial cells = Keratin

-Heart muscle cells = Desmin

CTC Immunoglobulin (Ig) Superfamily Proteins (ex: N-CAM)

Ca 2+ - independent

Weaker than cadherins

Homo and Heterophilic binding

CTC Selectins

In blood, Ca 2+ - dependent

Has Lectin domain = binds carbs

+ integrins = stronger hold: binds to proteins

Heterophilic binding

CTM Focal Adhesions

Link ECM proteins to cytoskeletal AFs

Binds cells to ECM

Integrin family (trans m)

Hemidesmosome

Links ECM proteins to cytoskeletal IFs

Attach epithelial cell to basal lamina

Occluding Junctions Function

Barrier to IF flow: compartmentalize

-Relatively impermeable

-Requires trans-cellular transport

Limit diffusion of M components

Occluding Junctions Structure

Membrane protein binding

Principle ones:

-Claudins (zipper-like)

Many types, variable permeability

-Occludins

Uncertain role

Channel-Forming Junctions Function

Cytoplasmic Connection- limited: ions and small molecules

Electrical and Chemical Coupling: synchronize responses

Channel-Forming Junctions Structure

Channel Composed by Connexins

6 Connexins =

-Connexon

-1/2 gap and 1/2 channels

**12 in all

Channel-Forming Junction Permeability

Varies

Regulated by EC signals

Decrease when pH decreases - unknown

Decrease when Cytosolic triple increase Ca 2+ Leaking

Signal-Relaying Junctions

Synapse

-Many cell adhesions acting together

-Scaffold Proteins

-Postsynaptic membranes

-Organize Complexes:

Connectors: Cadherin, Ig superfamily

Communicators: L-gated ion channels, NT receptors

Extracellular Matrix (ECM) Composition

Secreted by cell

-Proteins (fibers)

-Polysaccharides (ground substance)

Dominates connective tissue

-Blood

-Bones

-Fat

-Ex..

ECM Functions

Structural Support

-Physical Structure

-Orienting Cells

Fill Space

-Form Gels

-Regulate Molecular Traffic

Chemical Signaling

-Binding Growth Factors

-Cross-link Membrane Proteins

Regulate Secreted Proteins

-Immobilize, store, insulate, inactivate

-Ex. Inflammation

Most Common ECM Connective Cell

Fibroblast

Examples of Fibroblasts

Chondroblasts (form cartilage)

-Holds water

-Compressible

-Resilient

-Avascularized

Osteoblast (form bone)

-Mineral percipitation

-Highly vascularized

Fibroblasts

Locally produce matrix

Cytoskeleton aligns wit ECM fibers

Collagen Injections

Also Contains Elastin--- Elasticity

Protein Fibers

Collagen

Elastin

Fibronectin

Laminin

Collagen

Major Protein

Highly Abundant

Very Rigid and Stable (rope-like)

Collagen Structure

Triple Stranded Helix

Each Strand = Fribril

20 Types Based on 25 Fibrils

Collagen Orientation is Guided By?

Fibroblasts (Like the IF of the ECM)

Co-secreted Matrix Molecules

-Fibril-forming = Cables

-Fibril-associated = Link Fibrils and ECM

Elastin

Allows tissue to stretch and recoil- like a rubber band

Typically mixed with collagen

Fibronectin

Attaches cells to matrix

-Plasma Fibronectin - soluble

-Fibronectin-associated - between cell surface and ECM

Sequence Recognized by integrins

Laminin

Helps form Basal Lamino

-Mainly under Epithelium (muscle, fat)

-Regulate cell migration and orientation

Forming the Basal Lamino

Laminin

Integrin

Type IV Collagen

Perlecan

Nidogen

Polysaccharides

Glycosaminoglycans (GAGs)

Traits of GAGs

Long Sugar Chains

Repeating Dissaccharides

Lost of Negative Charge = Polar (like water)

Extremely Hydrophilic

-attract water

-take up space

-Turgid

GAG Examples

Hyaluronan

Proteoglycans

Hyaluronan

Simplest GAG; Atypical

Little Branching = Few Protein Links

Prevalent During Early Development

Readily Fills Space But Resists Compression

Proteoglycans

GAGs covalently linked to proteins (Ex. Aggrecan)

Functions Of Proteoglycans

Support

Filtering

Growth Factor Signaling

Regulate Secreted protein Activity

About this deck

By: Hannah Novinc
Created: 2012-02-14
Size: 35 flashcards
Views: 13

About StudyBlue

“I have used this website for three exams, and I see a huge difference in my test results.”
Naj