cell bio lecture 16

Adhesion receptors mediate what adhesions?

cell-matrix adhesions

the ECM is a dynamic, complex network or _____________ and ____________

proteins and polysaccharides

All animal cells can be classified as components of just five types of tissues:

1. Epithelial tissue 2. Connective tissue 3. Muscular tissue 4. Nervous tissue 5. Blood

each pore in the gap junctions consists of ___ connexin molecules, ______ from each cell

12 6

___ hemichannels interact to form a channel that bridges and connects the neighboring cells

2

classical cadherins possess ___ EC domains and a cytoplasmic domains that binds to a _________

5 catenin complex (binds to actin cytoskeleton)

______________ junctions allow movement of small molecules and ions between cytosols of adjacent cells

gap

_______________________ are sheet-like depositions of ECM on which various epithelial cells rest.

Basement membranes

integrins are large and diverse family, some can function as both ______________ and ___________

CAMs adhesion receptors

What type of interactions are necessary for assembling cells into tissues?

Cell-cell interactions Cell-extracellular matrix (ECM) interactions

neighboring cells are connected indirectly through their interactions with the

ECM

what can provide cells a pathway to migrate?

ECM (especially prevalent in metastasis of cancer cells)

Connective tissue, including tendons and cartilage, is composed mostly of _________________. it is packed with _______________ protein fibers

ECM (very few cells) insoluble

on classical cadherins, the Cytoplasmic domain binds to α-catenin which binds to ________ when under tension... links the cadherin to the cytoskeleton!

F-actin

________________ are large macromolecular assemblies through which mechanical force and regulatory signals are transmitted between the extracellular matrix (ECM) and an interacting cell.

Focal adhesions

to creat a collagen ECM network, We first synthesize collagen in the _____ as a precursor that cannot self assemble! This concept is known as a _______________.

RER propeptide

what is the common structural component of all cadherins?

The EC (extracellular cadherin) domain

the core unit of collagen IV is what

a monomer with two globular domains on the N and C terminus

There is a circumferential belt of ______ and _______ filaments associated with the ___________ junction - functions as a "tension cable" that controls cell shape

actin myosin adherens

the cytoplasmic domains usually link to ________________ (may functionally couple the CAM to the ________________)

adapter proteinscytoskeleton

what are the two types of anchoring junctions?

adherens junctions desmosomes

what type of molecule mediates cell- extracellular adhesion?

adhesion receptors

what can nidogens interact with

all the components of the basal lamina

what are the three major junctions that join cells together in the epithelial sheets using CAMs?

anchoring tight gap

tight junctions surround the cell below the __________ surface and connects to all neighboring cells

apical

tight junctions creates a boundary between________ and ___________ regions of the plasma membrane

apical basolateral

what three surfaces do epithilial cells have?

apical lateral basil

adhesion receptors mediate what>

attachment of cell to ECM

perlecan is a component of the

basal lamina

Often the lateral and basal surface are very similar in composition and are known as the ____________________ - in many ways, the basal and lateral sides are indistinguishable

basolateral surface

Interstitial connective tissue matrix is present where?

between the intercellular spaces

cadherins are _________ dependent adhesion molecules

calcium

in cadherins ___________ ions bind between individuals EC domains

calcium

what type of molecules mediate cell to cell interactions?

cell adhesion molecules (CAMs)

CAMs can also exhibit lateral interactions on the same cell, or___________ interactions

cis

often _____ interactions are first necessary before _____ interactions can occur

cis trans

what are the four groups cadherins can be classified into?

classical desmosomal protocadherins unconventional

anchoring adherens junctions use what CAMs? what type of cytoskeleton do they bind to? what interaction do they promote?

classical cadherins actin cell to cell

gap junctions are composed of (not conventionally known as a CAM because it forms a pore)

connexin

nidogens primarily act as

crosslinkers with the basal lamina

intergins typically possess a small __________ domain

cytoplasmic domain

what are the two specialized types of cadherins in desmosomes?

desmoglein desmocollin

anchoring desmosome junctions use what as the CAMs? what type of cytoskeleton do they bind to? what interaction do they promote?

desmosomal cadherins intermediate filament cell to cell

Cell-adhesion molecules (CAMs) mediate what adhesions?

direct cell-cell adhesions

ECM proteins bind to

each other and to cellular receptors

the extracellular portion of CAMs are also known as the

ectodomain

one of the defining features of animals is that the external and internal surfaces of most of their organs are built from tightly packed, sheet-like layers of cells known as _____________

epithelia

-CAMs mediate adhesion through their _______________ domain

exoplasmic

The ____________________ is a collection of extracellular molecules secreted by cells that provides structural and biochemical support to the surrounding cells.

extracellular matrix (ECM)

the major component of connective tissue is

fibrillar collagens

adhesion bonds are formed between the ____________________ of cadherins found on opposing membranes

first EC domains (EC1)

ECM can provide a reservoir of extracellular signaling molecules that control:

growth and development

6 connexins on the pore of one cell form a

hemichannel

on one side, the basil lamina is linked to cells by adhesion receptors including _____________________ and ___________________ that bind to the basal lamina. on the other side, it is anchored to adjacent connective tissue by a layer of ________________________ embedded in a proteoglycan-rich matrix

hemidesmosome integrins focal adhesion integrins collagen

intergins are found in what two things?

hemidesmosomes focal adhesions

when CAMs on one cell bind directly to a different type of CAM on another cell it is a __________ interaction

heterophilic

laminin is ______________________ multi adhesive matrix protein found in the basal laminae. it is made of what chains?

heterotrimeric alpha, beta, gamma chains

when CAMs mediate adhesion between cells that are different types it is

heterotypic

when CAMs on one cell bind directly to the same type of CAM on another cell it is a __________ interaction

homophilic

collagens can be composed of identical polypeptides (______________) or different polypeptides (_____________)

homotrimer heterotrimer

when CAMs mediate adhesion between cells of the same type it is

homotypic

what are the four major families of CAMs?

immunoglobin superfamily cadherins selectins intergrins (can function both as CAMs and as adhesion receptors

hemidesmosomes are small stud-like structures on the _____________ of epithelial cells

inner basal surface

The principal adhesion receptors for epithelial cells belong to the _______ family

integrin

hemidesmosomes use what adhesion receptors? what type of cytoskeleton do they bind to? what interaction do they promote?

integrins intermediate filaments cell to basal lamina

focal adhesions use what adhesion receptors? what type of cytoskeleton do they bind to? what interaction do they promote?

integrins actin cell to basil lamina

tight junctions use what CAMs? what type of cytoskeleton do they bind to? what interaction do they promote?

junctional adhesion molecule family (JAMs), occludins, and claudins actin cell to cell

what are the four ECM proteins found in the basal laminae?

laminin collagen type IV perlecan nidogen

folded procollagens will be transported to and through the golgi complex as ______________ but are still kept pretty small. the procollagen bundles are then secreted to the extracellular space and then N and C terminal propeptide sequences are removed by ___________________ to form mature protein. this starts self assembly. trimer assemble into covalently cross linked _____________

lateral associations proteolytic cleavages fibrils

what are some functions of the ECM

mechanical support, cushioning, adhesion

do gap junctions bind to any cytoskeletal elements?

no

is the collagen ECM network ever in the cell?

no

can integral membrane proteins freely migrate between apical and basolateral surfaces?

no the tight junction does not allow it

cadherins mediate adhesion between

opposing membrane surfaces

tight junctions regulate _____________ transport. it allows only small molecules to move from outside to inside.. all others must be transported by __________________ pathways

paracellular transcellular

gap junctions create _____________ that connects two neighboring cells together

pores

Propeptides associate to form disulfide-linked trimers to form _____________

procollagen

the circumferential belt resembles a ____________

sarcomere (can contract and change cell shape)

laminin ______________ into mesh like networks

self assembles

why is it that macro assembly will not happen with the propeptide collagens?

the N+C terminal ends prevent it. it has to be process before it becomes mature and can self assemble

the ECM is typically synthesized by what

the cells resting on it

the components of the ECM are

the interstital connective tissue matrix basement membrane

the extracellular matrix includes:

the interstitial connective tissue matrix (aka connective tissue) the basement membrane (aka the basal lamina).

are focal adhesions constant? do they change?

they are very dynamic, they are constantly disassembling and assembling in response to changes in the cell and ECM

what is the tight junctions job?

to seal off body cavities (seals the lumen of the intestine from the tissue below the intestinal epithelial

The CAM interactions that "bridge" neighboring cells together are known as _______ interactions

trans

CAMs are all _____________ proteins

transmembrane

integrins are ________________ proteins and function as

transmembrane obligate heterodimers (alpha and beta subunits)

collagens are made of __________ proteins made from _________ poolypeptides, each known as a ____ chain

trimeric 3 alpha

in collagen alphas chains come together to form

triple helical structure

t/f some CAMs can exhibit heterophilic and homophilic interactions

true

cadherins are ________________________ proteins

type 1 transmembrane