Cell Junctions and extra cellular matrix II

chapter 19

Desmosomes and hemidesmosomes both link to intermediate filaments

Cadherins also bind intermediate filaments together

Integrins link extracellular matrix to cytoskeleton

Size of gap junction channel can be determined with fluorescent molecules of different sizes

A Gap junction connexon is made up of 6 transmembrane connexin subunits

Images of gap junctions

The permeability of gap junctions can be regulated

dopamine treatment reduces permeability of gap junctions to a fluorescent dye

Summary of cell junctions found in the cell

Summary of cell junctions found in the cell

In plant cells plasmodesmata perform many of the same functions as gap junctions

View of plasmodesmata

Structure of Cadherin – responsible for cell to cell adhesion in vertebrate cells

Ca2+ is required to establish cell to cell connection through cadherin

Three mechanisms that mediate cell-cell adhesion

least commoncadherins

Cadherins allow cells to sort themselves

Catenins join cadherins to actin filaments in adherence junctions

Summary of junctional and non-junctional adhesive mechanisms

Cells surrounded by extracellular matrix

Cross sectional view of intestinal wall

Connective tissue underlying the epithelium contains a variety of cells and extracellular matrix components

Fibroblasts surrounded by collagen fibrils

Glycosaminoglycan (GAG) chains occupy large amounts of space and form hydrated gels

Hyaluronan, a simple GAG, occupies a large amount of space, thereby providing mechanical support

Repeating disaccharide unit of hyaluronan

GAG and its core protein form proteoglycan

Comparison of proteoglycans with a ribonuclease

picture of aggrecan aggregate, a large proteoglycan

structure of Aggrecan aggregate

Collagen fibril embedded in proteoglycan molecules

Fibroblast surrounded by collagen fibrils

Collagen fibrils in tadpole skin

This arrangementis also found in bone and the cornea

Elastic fibers in a dog’s aorta

Each elastin protein in the network can expand and contract as a coil

Fibronectin is an extracellular protein that helps cells attach to the matrix

Connective tissue underlying the epithelium contains a variety of cells and extracellular matrix components

basal lamina in the cornea of a chick’s embryo

A model of the basal lamina

Cross Section of Kidney

Filtration is one step in urine formation

Structure of Nephrons

Inside Bowman’s Capsule

Basal Lamina plays an important role in filtration