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