Download - ashish CELL ADHESION
-
8/7/2019 ashish CELL ADHESION
1/70
-
8/7/2019 ashish CELL ADHESION
2/70
CONTENT
CELL-CELL INTERACTION
CELL ADHESION
CADHERINS
SELECTIN
INTEGRINS
IMMUNOGOBULIN FAMILY
CELL JUNCTION
OCCULUDING JUNCTION
TIGHT JUNCTIONSEPTATE JUNCTION
ANCHORING JUNCTION
ADHEREN JUNCTION
FOCAL JUNCTION
DESMOSOMES
HEMI-DESMOSOMES
COMMUNICATING JUNCTION
GAP JUNCTION
PLASMDESMATA
CHEMICAL SYNPASES
SUMMARY
BIBLOGRAPHY
-
8/7/2019 ashish CELL ADHESION
3/70
-
8/7/2019 ashish CELL ADHESION
4/70
CELL ADHESION
Cell-cell adhesion is a selective process such that
cells adhere only to other cell of specific types.
This selectivity was first demonstrated in
classical studies of embryo development, whichshowed that cells from one tissue (e .g. liver)
specifically adhere to cell of the some tissue
rather than to cells of a different tissue (e.g.
brain).
Such selective cell-cell adhesion is mediated by
trans- membrane protein called cell adhesion
molecules (CAM)
-
8/7/2019 ashish CELL ADHESION
5/70
CELL ADHESION
TYPES OF CELL ADHESION
1. CELL-CELL ADHESION
2. CELL-EXTRACELLULAR MATRIX
-
8/7/2019 ashish CELL ADHESION
6/70
CELL ADHESION MOLECULES
Cell adhesion molecules are protein located on
the cell surface involved with the binding with
other cells or with the extracellular matrix
(ECM) in the process called cell adhesion.
Are typically trans-membrane receptor and are
composed of three domains : an intracellular
domains that interacts with cytoskeleton, a trans
membrane domain and an extracellular domain
that interacts with other CAMs of same kinds(hemophilic binding ) or with other CAMs or the
extracellular matrix (heterophilic binding)
-
8/7/2019 ashish CELL ADHESION
7/70
CELL ADHESION MOLECULES ARE DIVIDED
INTO FOUR MAJOR GROUPS
1. SELECTIN
2. INTEGRINS
3. CADHERINS
4.IMMUNOGLOBULIN SUPERFAMILY (Ig)
-
8/7/2019 ashish CELL ADHESION
8/70
CELL ADHESION INTERACTION HOMOPHILIC BINDING : Interaction in which an
adhesion molecule on the surface of one cell binds to thesame molecule on the surface of another cell.
HETROPHILIC BINDING : Interaction in which an
adhesion molecule on the surface of one cell recognizes a
different molecule on the surface of another cell (eg.
selectin and an integrin) LINKER DEPENDENT BINDING: Interaction of adjacent
cell adesion molecule on the surface of two cell binds with a
help of linker molecule.
-
8/7/2019 ashish CELL ADHESION
9/70
CADHERIN
Expressed in both invertebre and vertebrate
Are main molecules holding cells together in early
embryonic tissue
Homophilic binding
Calcium dependent
formation of adheren junction and desmosomes
Most cadherin are single pass trans-membrane
glycoproteins about 700-750 amino acid long.
They associate in the plasma membrane to formdimmers or larger oligomers as extracellular part of
the polypeptide chain which is usually folded into five
or six cadherin repeats, which are structurally related
to immunoglobulin (Ig) domains
-
8/7/2019 ashish CELL ADHESION
10/70
The Ca2+ ions are positioned between each pair
of cadherin repeats, locking the repeats together to
form a stiff, rod like structure: the more Ca2+ ions
that are bound, the more rigid the structure is.
If Ca2+ is removed, the extracellular part of
the protein becomes floppy and is rapidly degraded
by proteolytic enzymes
-
8/7/2019 ashish CELL ADHESION
11/70
THE LINKAGE OF CLASSICAL CADHERINS TO ACTIN FILAMENTS
THE CADHERINS ARE COUPLED INDIRECTLY TO ACTIN FILAMENTS BY
THE ANCHOR PROTEINS -CATENIN AND -CATENIN. ATHIRD
INTRACELLULAR PROTEIN, CALLED P120, ALSO BINDS TO
THE CADHERIN CYTOPLASMIC TAIL AND
REGULATES CADHERIN FUNCTION. -CATENIN HAS A SECOND, AND
VERY IMPORTANT, FUNCTION IN INTRACELLULAR SIGNALLING.
-
8/7/2019 ashish CELL ADHESION
12/70
Divided as classical and non-classical cadherin
Classical cadherin are E-cadherin, P-cadherin and N-
cadherin and are widely expressed during earlydifferentiation
E-cadherin is present in epithelial cells; N-cadherin
in nerve cells and P-cadherin in placenta and
epidermis. Non-classical cadherins include proteins with known
adhesive function such as desmosomal cadherins and
protocadherin found in brain
-
8/7/2019 ashish CELL ADHESION
13/70
SELECTIN
Single trans-membrane protein with highly
consereved lectin domain
Heterophilic binding
Calcium dependent cell-cell adhesion in the
bloodstream.
Three types of selectin: L-selectin in blood
cells(leukocytes), P-selectin in blood platelets and
E-selectin in endothelial cells
They are attached to actin filament with an
anchor protein they collaborate with integrins, which strengthen
the binding of the blood cells to the endothelium.
-
8/7/2019 ashish CELL ADHESION
14/70
(A) The structure of P-selectin. The selectin attaches to the actin
cytoskeleton through anchor proteins that are still poorly characterized.
(B) How selectins andintegrins mediatethecell-celladhesions
required
-
8/7/2019 ashish CELL ADHESION
15/70
Are active during inflammatory response
have an important role in binding white blood
cells to endothelial cells lining blood vessels,
thereby enabling the blood cells to migrate out of
the bloodstream into a tissue
-
8/7/2019 ashish CELL ADHESION
16/70
INTREGRIN Heterophilic binding
Present in verterbrates
At least 24 integrin heterodimer composed of 18 types
of subunits and 8 types of subunits in various
combination.
Integrin subunits span the plasma membrane and in
general have very short cytoplasmic domains of about
4070 amino acids where as beta-4 subunits have
1088 amino acid
The molecular mass of the integrin subunits can vary
from 90 kDa to 160 kDa Helps in focal adhesion and hemi-desmosomes
-
8/7/2019 ashish CELL ADHESION
17/70
-
8/7/2019 ashish CELL ADHESION
18/70
Protein named Talin activates the newly formed integrin
which is bent in position, attaches to the tail
Calcium and magnesium dependent It is hepls in formation of focal adhesion by forming a
complex of ligand, integrin molecule and associste plaques
protein
Not only do integrins perform this outside-in signalling,
but they also operate an inside-out mode. Thus,they transduce information from the ECM to the cell as
well as reveal the status of the cell to the outside, allowing
rapid and flexible responses to changes in the
environment, for example to allow blood coagulation by
platelets.
Integrins bind to extra-cellular proteins via short amino
acid sequences, such as the R-G-D sequence motif (found
in proteins such as fibronectin, laminin, or vitronectin)
-
8/7/2019 ashish CELL ADHESION
19/70
IMMUNOGLOBULIN SUPERFAMILY
categorized as members of this superfamily based on
shared structural features with immunoglobulins(also known as antibodies)
Calcium independent
Homophilic binding
Proteins of the IgSF possess a structuraldomain known as an immunoglobulin (Ig) domain.
contain about 70-110 amino acids and are categorized
according to their size and function
Ig-domains possess a characteristic Ig-fold, whichhas a sandwich-like structure formed by two sheets of
anti-parallel beta strands.
-
8/7/2019 ashish CELL ADHESION
20/70
-
8/7/2019 ashish CELL ADHESION
21/70
Among IgCAMs are neural CAMs, intercellular CAMs
(ICAMs) which function in the movement of leukocytes
into tissue and junction adhesion molecules (JAMs)
which are present in tight junction.
NCAMs play important role in he differentiation of
muscle, glial and nerve cell.
NCAMs comprises of extracellular region with five Ig
repeats and two fibronectin type III repeats, a singlemembrane-spanning segment and cytosolic segment
that interacts with the cytoskeleton.
In human, gene mutation in L1-CAM causes various
neuropathologies(e.g. mental retardation, congentialhydrocephalus and spasticity)
-
8/7/2019 ashish CELL ADHESION
22/70
CELL JUNCTION
Cell junction is a type of structure that existswithin the tissue of a multi-cellular organism.
They consist of protein complexes and provide
contact between neighboring cell or between a
cell and the extra cellular matrix or they buildupthe paracellular barrier of epithelia and control
the paracellular transport.
Cell junctions are especially abundant in
epithelial tissue.
-
8/7/2019 ashish CELL ADHESION
23/70
CELL JUNCTION CAN BE CLASSIFIED INTO
THREE FUNCTIONAL GROUP
OCCULUDING JUNCTION: Junction that seal celltogether in an epithelium in a way that prevents
even small molecule from leaking from one side
of the sheet to the other.
ANCHORING JUNCTION: Mechanically attachescell (and their cytoskeletons) to their neighbors or
to the extracellular matrix.
COMMUNICATING JUNCTION: Mediates the
passage of chemical or electrical signal from one
interacting cell to its proteins
-
8/7/2019 ashish CELL ADHESION
24/70
1.Occluding junctions
a.tight junctions
b.sepate junction2. Anchoring junctions
a. actin filamentattachmentsitesi. cell-cell adherens junctions (e.g., adhesion
belts)
ii. cell-matrix adherens junctions (e.g., focalcontacts)
b. intermediatefilamentattachmentsitesi. cell-cell adhesion (desmosomes)ii. cell-matrix adhesion (hemi-desmosomes)
3. Communicating junctionsa. gap junctionsb. chemical synapsesc. plasmodesmata (plants only)
-
8/7/2019 ashish CELL ADHESION
25/70
OCCLUDING JUNCTION
TIGHT JUNCTION:
present in vertebrates.
the epithelial cells lining the small intestine form a barrierthat keeps the gut contents in the gut cavity, the lumen.
the tight junctions between epithelial cells are thought tohave both of these roles.
first, they function as barrier to the diffusion of somemembrane proteins between apical and basolateraldomains of the plasma membrane. Mixing of such proteinand lipid occur if tight junction are disrupted by removingthe extra cellular Ca2+ that is required for tight junctionintegrity.
Second, tight junction seal neighboring cells together so
that if a low-molecular weight tracer is added to one side ofan epithelium, it will generally not pass beyond the tightjunction. Although all tight junction are impermeable tomacromolecule, their permeability to small molecule variesgreatly in different epithelia.
-
8/7/2019 ashish CELL ADHESION
26/70
SIMPLIFIED DRAWING OF A CROSS-SECTION THROUGH PART OF THE WALL
OF THE INTESTINE. THIS LONG, TUBELIKE ORGAN IS CONSTRUCTED
FROM EPITHELIAL TISSUES (RED), CONNECTIVE TISSUES (GREEN),
AND MUSCLE TISSUES (YELLOW). EACH TISSUE IS AN ORGANIZEDASSEMBLY OF CELLS HELD TOGETHER BY CELL-CELL ADHESIONS,
EXTRACELLULAR MATRIX, OR BOTH.
-
8/7/2019 ashish CELL ADHESION
27/70
Impermeable to macromolecule, their
permeability to small molecules varies greatly in
different epithelia. ability to restrict the passage of ions through the
spaces between cell is found logarithmically with
increasing number of strands in the network,thus
suggesting that strands acts as independentbarrier to ion flow
Major trans membrane protein are claudin and
occludin and also ZO which is essential for
formation of and function of tight junction.
-
8/7/2019 ashish CELL ADHESION
28/70
Role of tight junction in transcellular protein: Transport proteins are confined to different regions of the
plasma membrane in epithelial cells of the small intestine. This segregation permits a vectorial transfer of
nutrients across the epithelial sheet from the gut lumen to the blood. In the example shown, glucose is
actively transported into the cell by Na+-driven glucose symports at the apical surface, and it diffuses out of
the cell by facilitated diffusion mediated by glucose carriers in the basolateral membrane. Tight junctions are
thought to confine the transport proteins to their appropriate membrane domains by acting as diffusionbarriers within the lipid bilayer of the plasma membrane; these junctions also block the backflow of glucose
from the basal side of the epithelium into the gut lumen
-
8/7/2019 ashish CELL ADHESION
29/70
DISORDER RELATED TO TIGHT JUNCTION
Disruption of TJs leads to intestinal
hyperpermeability (the so-called "leaky gut")
which has been proposed by some researchers to
involve a relationship with acute and chronic
diseases such as systemic inflammatory response
syndrome (SIRS frequently a response of theimmune system to infection), inflammatory bowel
disease, type-1 diabetes, allergies, asthma,
and autism(impaired social interaction and
communication and restricted and repetative
behaviour)
-
8/7/2019 ashish CELL ADHESION
30/70
SEPTATE JUNCTION
Discovered by R.L. Wood 1959 found in invertebrate tissues adhesion, sealing,
communication septa walls regularly spaced
cross bars 15-17 nm .
This are main occluding junction in invertebrates
regular in structure than a tight junction , they
likewise form continuous band around each
epithielial cell. But their morphology is proteins
that are arranged in parallel rows with a regular
periodicity .
-
8/7/2019 ashish CELL ADHESION
31/70
Electron micrograph of a septate junction between two epithelial cells of a
mollusk. The interacting plasma membranes, seen in cross-section, are
connected by parallel rows of junctional proteins. The rows, which have aregular periodicity, are seen as dense bars or septa. (From N.B. Gilula, in
Cell Communication [R.P. Cox, ed.], pp. 1-29)
-
8/7/2019 ashish CELL ADHESION
32/70
A protein called Disc-large, which is required for
the formation of septate junction in Drosophila is
structurally related to the ZO protein found invertebrate tight junction.
Mutant flies that are deficient in this protein not
only lack septate function but also develop
epithelial tumors.
This observation suggests that the normal
regulation of cell proliferation in epithelial tissue
may depend in part on intra cellular signal that
emanate from occluding junction.
-
8/7/2019 ashish CELL ADHESION
33/70
ANCHORING JUNCTION
widely distributed in animal tissue and are most
abundant in tissue that are subjected to serve
mechanical stress such as heart, muscle and
epidermis.
composed of two main classes of protein-Intra
cellular anchor protein and Trans-membrane
adhesion proteins.
-
8/7/2019 ashish CELL ADHESION
34/70
-
8/7/2019 ashish CELL ADHESION
35/70
Intracellular anchor protein:
proteins form a distinct plaque on thecytoplasmic face of the plasma membrane and
connect the junctional complex to either actin
filaments or intermediate filaments.
Trans-membrane adhesion protein :
protein have a cytoplasmic tail that binds to one
or more intracellular anchor protein and an
extracellular domains that interacts with either
the extracellular matrix or the extracellular
domains of specific trans-membrane adhesionprotein on another cell.
-
8/7/2019 ashish CELL ADHESION
36/70
-
8/7/2019 ashish CELL ADHESION
37/70
-
8/7/2019 ashish CELL ADHESION
38/70
Dependingupon Cytoskeletonattachment
sites anchoring junctionisclassifiedas
A). Actin filament attachment sites
1. adherens junction
2. focal adhesion
B). Intermedite filament attachment sites
1. Desmosomes
2. Hemi-desmosomes
-
8/7/2019 ashish CELL ADHESION
39/70
-
8/7/2019 ashish CELL ADHESION
40/70
-
8/7/2019 ashish CELL ADHESION
41/70
FOCAL ADHESION Integrin mediated junction
Enable cells to get hold on the extra-cellular matrixthrough integrins that link intra cellularly to actinfilaments .In this way muscle cells for example attachto their tendous at the myotendinous junction.
Likewise, when cultured fibroblast migrates on an
artificial substratum coated with extra-cellularmatrix molecules, they also grip the substratum atfocal adhesion where bundle of actin filamentterminate.
At all such adhesion , the extracellular domains oftrans-membrane integrin protein bind to a proteincomponent of the extra-cellular matrix , while theirintra-cellular domain bind indirectly to bundles ofactin filament via the intra-cellular anchor proteintalin, -actinin, filamin and vinculin.
-
8/7/2019 ashish CELL ADHESION
42/70
-
8/7/2019 ashish CELL ADHESION
43/70
Function as signal carriers (sensors), which
inform the cell about the condition of the ECM
and thus affect their behavior
important role in the immune system, in which
white blood cells migrate along the connective
endothelium following cellular signals and to
damaged biological tissue Also active signalling during cell motility to cell
cycle
-
8/7/2019 ashish CELL ADHESION
44/70
DESMOSOMES Discovered by K.R. Porter in 1954
Homophilic interaction between trans-membraneprotein(Cadherin)
Through desmosomes the intermediate filament of
adjacent cell are linked into a net that extends
throughout the many cell of a tissue . The particular type of intermediate filament attached
to the desmosomes depend on cell type: they are
keratin filament in heart muscle cells .
The junction has a dense cytoplasmic plaque
composed of a complex of intra cellular anchor
proteins (plakoglobin and desmoplakin) that are
responsible for connecting the cytoskeleton to the
trans-membrane adhesion proteins.
-
8/7/2019 ashish CELL ADHESION
45/70
-
8/7/2019 ashish CELL ADHESION
46/70
-
8/7/2019 ashish CELL ADHESION
47/70
Found in muscle cells
Blistering diseases such as Pemphigus vulgaris
or Pemphigus foliaceus can be due to genetic
defects in desmosomal proteins.(epithelial cells of
skin)
patients who suffer from autoimmune diseases
characterized by skin and mucous membraneblistering produce autoantibodies against
desmogleins 1 and 3 (DSG1, DSG3). These two
observations suggested that the loss of normal
desmosome function could lead to tissue fragility
disorders.(cadherin based protein desmoglein and
desmocolin)
-
8/7/2019 ashish CELL ADHESION
48/70
HEMI-DESMOSOMES This are half-desmosomes resemble desmosomes
morphologically and in connecting tointermediate filament and like desmosomes they
act as rivets to distribute tensile or shearing
forces through an epithelium .Instead of joining
adjacent epithelial surface of an epithelial cell to
underlying basal lamina. The extracellular domains of the integrins that
mediate the adhesion bind to laminin protein in
the basal lamina while an intracellular domain
binds via an anchor protein (plectin) to keratinintermediate filaments.
-
8/7/2019 ashish CELL ADHESION
49/70
-
8/7/2019 ashish CELL ADHESION
50/70
DISORDER DUE TO HEMI-DESMOSOMES
Epidermolysis Bullosa is a set of geneticallyinherited conditions affecting 1 in 17,000 of the
population. A fault in a gene causes the skin to be
extremely fragile. The layers of the skin do not
adhere properly and painful widespread blisters
occur very easily. These can lead to increasing
disfigurement, disability and in the most severe
forms death in early childhood.
Genes encoding different components of
hemidesmosomes have been found to be mutatedin various forms of hereditary bullous skin
disorders
-
8/7/2019 ashish CELL ADHESION
51/70
Table 19-2 Anchoring Junctions
Junction
Transmembrane Linker
Protein Extracellular Ligand
Intracellular
Cytoskeletal
Attachment
Some Intracellular
Attachment Proteins
Adherens
(cell-cell)
cadherin (E-cadherin) cadherininneighboring
cell
actin
filaments
catenins, vinculin, -
actinin, plakoglobin
Desmosome cadherin (desmogleins
& desmocollins)
cadherininneighboring
cell
intermediate
filaments
desmoplakins,
plakoglobin
Adherens
(cell-matrix)
integrin extracellularmatrix
proteins
actin
filaments
talin, vinculin, -actinin
Hemidesmos
ome
integrin extracellularmatrix (basal
lamina) proteins
intermediate
filaments
desmoplakinlike protein
-
8/7/2019 ashish CELL ADHESION
52/70
Gap junctions as seen in the electron microscope Thin section (A) and freeze
-
8/7/2019 ashish CELL ADHESION
53/70
Gap junctions as seen in the electron microscope. Thin-section (A) and freeze-
fracture (B) electron micrographs of a large and a small gap junction between fibroblasts
in culture. In (B) each gap junction is seen as a cluster of homogeneous intra-membrane
particles associated exclusively with the cytoplasmic fracture face (P face) of the plasma
membrane. (From N.B. Gilula, in Cell Communication [R.P. Cox, ed.], pp. 1-29)
-
8/7/2019 ashish CELL ADHESION
54/70
Permits the passage of molecules as large as 1.2 nm
in diameter (mammalian) and 2 nm in insects
Molecules smaller than 1200 Da can pass but lager
than that wont
Thus ion, low-molecular weight precursors of
cellular macromolecules, products of intermediary
metabolism and small intracellular signalingmolecules can pass
Gap junction composed of connexins, a family of
structurally related trans-membrane proteins which
consist of 21 different human protein. Innexins forms gap junction in invertebrates
-
8/7/2019 ashish CELL ADHESION
55/70
Determining the size of a gap-junction channel. When
fluorescentmoleculesof varioussizes areinjectedintooneoftwo
cellscoupledby gap junctions, moleculessmallerthan about 1000daltons can passintotheothercellbutlargermoleculescannot.
-
8/7/2019 ashish CELL ADHESION
56/70
Vertebrate hexagonal particle consists of 12
connexin molecules: 6 of the molecules are
arranged in connexon hemi-channel
Hexagonal cylinder of one plasma membrane
when joined to adjacent cell hemi-channel they
form a continuous aqueous channel between the
cell
Homotypic connexon : single type of connexin
Hetero-oligomeric connexon : two or more type of
connexin
plays a crucial role in the maintenance of
homeostasis, morphogenesis, cell differentiation,and growth control in multicellular organisms
-
8/7/2019 ashish CELL ADHESION
57/70
AMODEL OF A GAP JUNCTION. THE DRAWING SHOWS THE INTERACTING PLASMA
MEMBRANES OF TWO ADJACENT CELLS. THE APPOSED LIPID BILAYERS (RED) ARE
PENETRATED BY PROTEIN ASSEMBLIES CALLED CONNEXONS(GREEN),EACH OF
WHICH IS THOUGHT TO BE FORMED BY SIX IDENTICAL PROTEIN SUBUNITS
(CALLED CONNEXINS). TWO CONNEXONS JOIN ACROSS THE INTERCELLULAR GAP
TO FORM A CONTINUOUS AQUEOUS CHANNEL CONNECTING THE TWO CELLS.
-
8/7/2019 ashish CELL ADHESION
58/70
Gap junctions are not always open
Opening & closing is regulated by changes in pH
and Ca2+ concentration
High Ca2+, Low pH closed
Low Ca2+, high pH open
-
8/7/2019 ashish CELL ADHESION
59/70
DISORDERS IN GAP JUNCTION
Connexin 32 mutations cause X-linked Charcot-
Marie-Tooth disease, an inherited peripheraldemyelinating neuropathy.
Connexin 26 mutations have been found in hereditary
nonsyndromic sensorineural deafness. Connexin 43
knockout mice die shortly after delivery because of
cardiac malformation.
Neuronal gap junctions are involved in electrical
coupling and may also contribute to the recovery of
function after cell injury. Astrocytes are involved in
the pathology of most neuronal disorders, includingbrain ischemia, Alzheimer's disease and epilepsy.
In the pathology of brain tumors, gap junctions may
be related to the degree of malignancy and metastasis
-
8/7/2019 ashish CELL ADHESION
60/70
PLASMODESMATA
Plays a key role in plant development
Adhesion between plant cells is mediated by their cellwalls rather than by trans-membrane proteins. Inparticular, specializes pectin-rich region of the cellwall called the middle lamella acts as a glue to holdadjacent cells together.
Because of the rigidity of plant cell walls, stable
association between plant cells do not require theformation of cytoskeleton links such as those providedby the desmosomes and adherens junction of animalcells.
adjacent plant cell communicate with each otherthrough cytoplasmic connection called plasmodesmata
(singular, plasmodesma). Although distinct in structure, plasmodesmata
function analogously to gap junction as means ofdirect communication between adjacent cells intissues.
PLASMODESMATA (A) THE CYTOPLASMIC CHANNELS OF PLASMODESMATA
-
8/7/2019 ashish CELL ADHESION
61/70
PLASMODESMATA. (A) THE CYTOPLASMIC CHANNELS OF PLASMODESMATA
PIERCE THE PLANT CELL WALL AND CONNECT ALL CELLS IN A PLANT
TOGETHER. (B) EACH PLASMODESMA IS LINED WITH PLASMA MEMBRANE
COMMON TO TWO CONNECTED CELLS. IT USUALLY ALSO CONTAINS A FINE
TUBULAR STRUCTURE(20-40
NM),
THE DESMOTUBULE,
DERIVED FROM
SMOOTH ENDOPLASMIC RETICULUM
-
8/7/2019 ashish CELL ADHESION
62/70
An extension of the smooth endoplasmic
reticulum passes through the pore, leaving a ring
of surrounding cytoplasm through which ions and
small molecules are able to pass freely betweenthe cells.
Extension of endoplasmic reticulum called as
desmotubule
Permits a passage of 10,000 Da Increase conc. of Ca2+ affects permeability,
reverse inhibiting movement of molecules
Molecules like protein, nucleic acids, metabolic
product and plant virus pass throughplasmadesmota also membrane bound molecules
-
8/7/2019 ashish CELL ADHESION
63/70
-
8/7/2019 ashish CELL ADHESION
64/70
CHEMICAL SYNAPSES
The term was introduced by British
neurophysiologist Charles Sherrington, whoargued, on the basis of his own observations ofreflex responses and the studies of the greatSpanish anatomist, Ramny Cajal,
Serves as one-way communication devices,
transmitting information in one direction only Consist of pre-synaptic cell which transmits
information to post-synaptic cell which recievesinformation
Pre-synaptic cell and post-synaptic cell are areseparated by minute gap called synaptic cleft
Neurotransmitter act as median fortransmission
-
8/7/2019 ashish CELL ADHESION
65/70
-
8/7/2019 ashish CELL ADHESION
66/70
Binding of neurotransmitter molecule produces a
change in the three-dimensional shape of the
receptors that opens a tiny intrinsic pore in the
protein.
Major neurotransmitters:
Amino acids: glutamate, aspartate, D-serine, -
aminobutyric acid (GABA), glycine
Monoamines and other biogenic amines: dopamine
(DA), norepinephrine (noradrenaline; NE, NA),
epinephrine (adrenaline), histamine, serotonin (SE,
5-HT), melatonin
Others: acetylcholine (ACh), adenosine, anandamide,nitric oxide
-
8/7/2019 ashish CELL ADHESION
67/70
-
8/7/2019 ashish CELL ADHESION
68/70
SUMMARY What is cell adhesion and its role
Types of cell adhesion Cell adhesion and its molecules (CAM)
integrin, selectin, cadherins and immunglobulin
superfamily
Cell Junctiongap junction, septate junction
anchoring junction (adherens and focal ) and
(desmosomes and hemi-desmosomes)
Gap junction plasmadesmota and chemicalsynapses
-
8/7/2019 ashish CELL ADHESION
69/70
BIBLOGRAPHY
Bruce Alberts, Dennis Bray, Karen Hoplein,
Alexander Johnson, Julian Lewis, Martin Raff,
Keith Roberts and Peter Walter. (2004).
Molecularbiology ofthecell , Ed:4, Garland
science publications, New York,
Geoffery M. Cooper, Robert E. Hausman (2009).The Cell A Molecular Approach, Ed:4, ASM
Press and Sinauer Associates, Inc.
Gerald Karp (2002) Celland Molecular
Biology Conceptand Experiment, Ed: 3,page no: 258-268
-
8/7/2019 ashish CELL ADHESION
70/70
THANK YOU