Chapter 6 - Integrating Cells into Tissues

Dystroglycan

________ is synthesized as a large glycoprotein precursor that is proteolytically cleaved into two subunits.

Tight junctions

________ prevent the diffusion of macromolecules and to varying degrees impede the diffusion of small water- soluble molecules and ions across an epithelial sheet in the spaces between cells.

Collagen fibers

________, which provide mechanical strength and resilience.

Desmosomes

________ and hemidesmosomes also transmit shear forces from one region of a cell layer to the epithelium as a whole.

Extravasation

________ requires the successive formation and breakage of cell- cell contacts between leukocytes in the blood and endothelial cells lining the vessels.

Entactin

________ (also called nidogen), a rod- like molecule that cross- links type IV collagen and laminin and helps incorporate other components into the ECM.

Fibronectins

________ help attach cells to the extracellular matrix by binding to other ECM components.

leakiness of tight junctions

The ________ can be altered by intracellular signaling pathways, especially G protein- coupled pathways entailing cyclic AMP and protein kinase C Many Cell- Matrix and Some Cell- Cell Interactions Are Mediated by Integrins.

Multiple O

________- linked oligosaccharides are attached covalently to side- chain hydroxyl groups of serine and threonine residues in the subunit.

Microscopy

________ and other experimental approaches (e.g., biochemical binding experiments) have demonstrated the role of integrins in cross- linking fibronectin and other ECM components to the cytoskeleton.

elastin fibers

Rubberlike ________, which can be stretched and relaxed, also are present in deformable sites (e.g., skin, tendons, heart) Formation of Collagen Fibrils in the Endoplasmic Reticulum and Is Completed Outside the Cell.

indoleacetic acid

The amount, type, and direction of plant cell growth are regulated by small- molecule hormones (e.g., ________) called auxins.

nervous tissue

In ________, some neurons are connected by gap junctions through which ions pass rapidly, thereby allowing very rapid transmission of electrical signals.

Golgi

Unlike cellulose, pectin and hemicellulose are synthesized in the ________ apparatus and transported to the cell surface where they form an interlinked network that helps bind the walls of adjacent cells to one another and cushions them.

ECM

The binding of certain ________ molecules or CAMs on other cells to the bent, low- affinity structure would force the molecule to straighten and consequently separate the cytoplasmic tails.

adult organisms

In ________, several types of white blood cells (leukocytes) participate in the defense against infection caused by foreign invaders (e.g., bacteria and viruses) and tissue damage due to trauma or inflammation.

Cadherins

________ are key molecules in cell- cell adhesion and cell signaling, and they play a critical role during tissue differentiation.

protective surfaces

Stratified (multilayered) epithelia commonly serve as barriers and ________ (e.g., the skin)

disulfide bonds

Fibronectins are dimers of two similar polypeptides linked at their C-termini by two ________; each chain is about 60- 70 nm long and 2- 3 nm thick.

Plant tissues

________ are organized into just four main organ systems.

auxin

The ________- induced weakening of the cell wall permits the expansion of the intracellular vacuole by uptake of water, leading to elongation of the cell.

self association

The force needed to unfold and expose functional ________ sites in fibronectin is much less than that needed to disrupt fibronectin- integrin- binding.

viscous proteoglycans

Highly ________, a group of glycoproteins that cushion cells and bind a wide variety of extracellular molecules.

LG domains

________ are found in a wide variety of proteins and can mediate binding to steroids and proteins as well as carbohydrates Secreted and Cell- Surface Proteoglycans Are Expressed by Many Cell Types.

Syndecans

________ are expressed by epithelial cells and many other cell types.

plasma membrane

When the ________ is purified and then sheared into small fragments, some pieces mainly containing patches of gap junctions are generated.

Epithelia

________ in different body locations have characteristic morphologies and functions.

Stems

________ have support and transport functions; roots provide anchorage and absorb and store nutrients; leaves are the sites of photosynthesis, and flowers enclose the reproductive structures.

VI

Type ________ collagen is unusual in that the molecule consists of a relatively short triple helix with globular domains at both ends.

morphogenesis

First expressed during ________, NCAMs play an important role in the differentiation of muscle, glial, and nerve cells.

Integrin

________ containing adhesive structures have been studied most frequently in fibroblasts grown in cell culture on flat glass or plastic surfaces (substrata)

Hemidesmosomes

________ found mainly on the basal surface of epithelial cells, anchor an epithelium to components of the underlying extracellular matrix.

transmembrane glycoproteins

Like other secreted and ________, proteoglycan core proteins are synthesized on the endoplasmic reticulum.

laminin

Mutations in dystrophin, other DGC components, ________, or enzymes that add the O- linked sugars to dystroglycan disrupt the DGC- mediated link between the exterior and the interior of muscle cells and cause muscular dystrophies Ca2+- Independent Cell- Cell Adhesion in Neuronal and Other Tissues Is Mediated by CAMs in the Immunoglobulin Superfamily.

type II collagen

The fibrils of ________, the major collagen in cartilage, are smaller in diameter than type I fibrils and are oriented randomly in a viscous proteoglycan matrix.

three-dimensional ECM

When fibroblasts are cultured in ________ matrices derived from cells or tissues, they form adhesions to the ________ substratum, called 3D adhesions.

IV

Type ________ collagen, trimeric molecules with both rodlike and globular domains that form a two- dimensional network.

numerous homologous proteins

The claudin multigene family encodes ________ (isoforms) that exhibit distinct tissue- specific patterns of expression.

family of multi-adhesive proteins

Laminins, a(n) ________ that form a fibrous two- dimensional network with type IV collagen and that also bind to integrins.

basal lamina

In animals, epithelia and most organized groups of cells are underlain or surrounded by the ________, a sheetlike meshwork of ECM components usually no more than 60- 120 nm thick.

Glycine

________ is essential because its small side chain, a hydrogen atom, is the only one that can fit into the crowded center of the three- stranded helix Laminin, a Multiadhesive Matrix Protein, Helps Cross- link Components of the Basal Lamina.

extracellular matrix

Is one of more than 20 types of collagen that participate in the formation of the ________ in various tissues.

extracellular hormonal signals

Some ________ induce the production or release of small intracellular signaling molecules called second messengers that regulate cellular metabolism.

Proteoglycans

________ are a subset of glycoproteins containing covalently linked specialized polysaccharide chains called glycosaminoglycans (GAGs), which are long linear polymers of specific repeating disaccharides.

ECM components

Changes in ________, which are constantly being remodeled, degraded, and resynthesized locally, can modulate the interactions of a cell with its environment Diversity of Animal Tissues Depends on Evolution of Adhesion Molecules with Various Properties.

Arabidopsis proteins

________ have a single transmembrane domain and an intracellular cytosolic tyrosine kinase domain.

Soluble multi-adhesive matrix proteins

________, which bind to and cross- link cell- surface adhesion receptors and other ECM components The Basal Lamina Provides a Foundation for Epithelial Sheets.

tight adhesion

For ________ to occur between activated endothelial cells and leukocytes, B2- containing integrins on the surfaces of leukocytes also must be activated by chemokines or other local activation signals such as platelet- activating factor.

GAGs

________ are classified into several major types based on the nature of the repeating disaccharide unit: heparan sulfate, chondroitin sulfate, dermatan sulfate, keratan sulfate, and hyaluronan.

GAG chains

The arrangement of the sugar residues in ________ and the modification of specific sugars (e.g., the addition of sulfate) in the chains can determine their function and that of the proteoglycans containing them.