Cell Cell Interaction
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Transcript of Cell Cell Interaction
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CELL-CELLINTERACTION
Evy Sulistyoningrum
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Introduction
Cells of multicellular organism communicate each other
Coordinate integrated function
Communication between cells:
Releasing signal molecules Cells receptor proteinspecific
Cell signaling:
Autocrine signaling
Direct contacts
Paracrine signaling
Endocrine signaling
Synaptic signaling
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Means of cell signaling
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Speficity of cells receptor
protein
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Cells receptor protein
Intracellular receptor
Cytoplasm or nuclear
receptor
Lipid soluble signalsEx: steroid hormone,
vitamin D, etc
Mechanism of action:
Gene regulators
Enzymes
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Cells receptor protein
Cell surface receptor
Water soluble signals
Converts extracellular to intracellular signals
3 class of cell surface receptors:Chemically gated ion channels
Enzyme-linked receptors
G-protein linked receptorMost abundant
7 trans-membrane protein linked with GTP-
binding protein
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Cells surface receptor
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G-protein linked receptor
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Second messengers
Second messengers : intracellular mediators
Substances that relay receptors to target protein
Most widely used:
Cyclic adenosine monophosphate (cAMP)
Produced by adenylil cyclase
Calcium
Stored in RECalmodulin helps activated target protein
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How 2nd messengers work?
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Signal amplification
Low signals must be amplified to acquiredadequate response
Tyrosine kinases
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Direct contacts
Direct contact between cells surfaces
Cell junctions: long-lasting
interactions/permanent contacts between cells
Types of direct contacts:
Tight junctions
Anchoring junctions
Communicating junctions
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Direct contacts
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Tight junctions
Occluding junctions: Zonula Occludens
Connects plasma membrane of adjacent cells in
a sheet
Locate at the very apical end of junctionalcomplexes between cells
Functions:
Form a selective permeability barrieracrossepithelial sheet
Seals off body cavities such as intestine, stomach
lumen, bile duct, blood-brain barrier, etc.
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Tight junction
Structure of tight junction as a honeycomb-likenetwork of ridges & grooves
Linkage of rows of protein particles (3-4 nm )
Major proteins: occludin, claudin-1, JAM(junction adhesion molecule)
Prevents the diffusion of macromoleculesacross epithelial sheet
Prevents diffusion of membrane proteins andglycolipids between the apical and thebasolateral regions of the plasma membrane
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Alberts et al., 2002
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Alberts et al., 2002
The role of tight junctions in allowing epithelia
to serve as barriers to solute diffusion
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Anchoring junctions
Specialized region on the cell surface
Contains cell-adhesion molecules oradhesionreceptors that interact with other cells or the
extracellular matrix and with cytoskeletal fibersCommon in tissues exposed by mechanical stress, ex:
muscle, skin
Major types:
Adherens junctions (zonula adherens)Desmosomes (macula adherens)
Hemidesmosomes
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Adherens Junctions
Also known aszonula adherens
A type of specialized adhesive junction,
partially common in epithelia
Plasma membranes of adjacent cells are
connected by cadherins orother cell adhesion
molecules (e.g., integrins)
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Alberts et al., 2002
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Lodish et al., 2004
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Alberts et al., 2002
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Desmosome
macula adherens
Disc-shaped adhesive junction (~1 mm diameter)
Located basal to adherens junction
Contains desmogleins & desmocollins
(desmosomal cadherins)
Found in variety of tissues (need mechanical
strength: e.g., cardiac muscle & epithelia of skinand uterine cervix)
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Desmosomes
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Desmosome
Inner surface of plasma membrane: dense cytoplasmic
plaques
As site of anchorage for looping intermediate filaments
that extend into the cytoplasmcontains desmoplakins & plakoglobin (adaptor proteins
that link desmosomal cadherins to intermediate filaments
)
3-D network of intermediate filaments provides structural
continuityand tensile strength to the entire sheet of cells
Pemphigus vulgaris : has antibody against one of his/her
own desmo leins loss of e idermal cell-cell adhesion
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Pemphigus vulgaris
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Hemidesmosome
Half desmosome
Specialized adhesive structure at the basal
surface of epithelial cells
Function: attach the cells to their underlying
basement membrane (basal lamina)
Contains a dense plaque on the innermembrane, with keratin-containing
intermediate filaments coursing out into the
cytoplasm
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Lodish et al., 2004
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Karp, G., 2005
a b
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Communicating junctions
Passageways between cells that allow transferof chemical or electrical signals
Types:
Plasmodesmata: plantsGap junctions: animal
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Gap Junctions
Sites between animal cells that are specialized for
intercellular communication
Span the adjacent plasma membranes with very fine
molecular pipelines that allow the passage of smallmolecules (1000 daltons)
Electrical & metabolic couplings
RegulationpH: Low pH closes
Calcium: High calcium closes
Extracellular signals: Dopamine closes
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Gap junction
Gap junctions are constructed from transmembrane
protein called connexin
Six identical protein subunits assemble to form a
structure called connexonTwo connexons from adjacent plasma membranes
align to form a continuous aqueous channelof gap
junction
Gap junctions in different tissues can have different
permeability due to difference in connexin (there are
at least 11 distinct connexins)
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Gap
Junctions
Comprised of
connexons
Connexons
made
of connexins
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A summary of various cell junctions found in vertebrate
epithelial cells
Alberts et al., 2002
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Paracrine signaling
Signal molecules released by cells diffuse
through the extracellular fluid to other cells
Molecules are taken up by neighboring cells or
quickly removed Influence is restricted to cells in the immediate
vicinity of the releasing cell
short-lived, local effects Early development, coordinating the activities
of clusters of neighboring cells
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Paracrine signaling
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Endocrine signaling
Released signal molecule enterthe organismscirculatory system travel widely throughout
the body.
Longer lived signal molecules May affect cells very distant from the releasing
Cell
Signal molecules: hormones Endocrine system
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Endocrine signaling
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Synaptic signaling
Cells of the nervous system provide rapid
communication with distant cells.
Signal molecules travel through long, fiberlike
extensions of nerve cells from their tips veryclose to the target cells
Signal molecules (neurotransmitters)
The narrow gap between the two cells :
chemical synapse
Neurotransmitters cross the synapse and persist
only briefly
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Synaptic signaling
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Thank you..