CELL JUNCTIONS AND CYTOSKELETON

DR NILESH KATE
MBBS,MD
PROFESSOR
DEPT. OF PHYSIOLOGY
CELL
JUNCTIONS.

OBJECTIVES.
At the end of the class, you must know
 Cytoskeleton
 Molecular motors
 Intercellular communication.
 Enumerate the different types of intercellular
communications.
 Cell adhesion molecules

Cytoskeleton
 Essential elements
 Provide shape, movements & anchorage to
the cells..
Tuesday, December 6, 2022

Types.
 Microtubules
 Microfilaments
 Intermediate filaments.

Microtubules
 Largest cytoskeletal
structure.
 Composed of pairs of
tubulin protein
molecules.
 Maintain overall shape
of cell like steel beam
of a building.

Microtubules
 Forms a dense network
spread across the cell.
 Also functions as a
transport system.
 Motor proteins walk
along the microtubules.
 Movement of
chromosomes in cell
division.

Microtubules
 Movement of entire
cells.
 Cilia – bundles of
microtubules.(motility)
 Flagella – long bundles
of microtubules that
moves the cell.

Microfilaments
 Actin & myosin–
maintain & change cell
shape.
 Helps cells moves by
changing shape. Eg-
Amoeba (Pseudopodia)
 Movements within cells
by current of cytoplasm
(plant – photosynthesis)

Intermediate filaments.
 10nm – avg diameter.
 Also contribute to
maintain shape.
 Less dynamic but
more stability.
 Position of nucleus..

Molecular motors
 Helps in movements of
proteins, organelle &
cell parts
 2 domains –
 Cargo –
 Roads – microtubules.
 Types
 Microtubule based
 Actin based.

Molecular motors
 Microtubule based
 Conventional kinesin
 Dyneins
 Actin based
 Myosin

Intercellular communication.
 Unicellular organisms
 Multi-cellular organism
 Cells- tissue – organs- system – body.
 Need –
 Communication
 Shape – (Cytoskeleton)
 Support
 Special functions.

Intercellular junctions
 Cell adhesion molecules
 Prominent parts of intercellular connections by
which attached to basal lamina and to each other.

TYPES
 Cadherins
 Adhesion molecules of IgG subfamily
 Selectins
 Integrins

TYPES
 Cadherins – Ca dependent molecules mediate
cell to cell adhesion through homophilic
binding.
 Adhesion molecules of IgG subfamily – IgG
immunoglobulins binds to various antigens
 Selectins – lectin like domains binds to
carbohydrates.
 Integrins – heterodimers that binds to various
receptors.

Mechanism of adhesion
 Homophilic binding – to like moleccules
 Heterophilic binding – to different
molecules.
 Anchorage with cytoskeleton – inside the
cell
 Binding to laminins – family of large cross
shaped molecules to receptor domains.

Functions of cell adhesion
molecules
 Signal transmission in & out of cell.
 Nervous system – Embyonic development &
formation.
 Tissue holding
 Inflammation & wound healing
 Metastasis of tumour

Types of intercellular
junctions
 Tight junctions
 Adherens
junctions
 Gap junctions

TIGHT JUNCTIONS
 Called Zona occludens
or occluding zone
 Outer layer of PL fused
with each other
 Obliterate the space
between cell
 Does not allow
transport/movement of
ions or other solutes.

Example
 Blood brain barrier
 Blood retinal
barrier.
 Intestinal mucosa.
 Blood testes barrier

ADHERENS JUNCTIONS
 Zona adherens
 Cell adhere to each
other by dense
accumulation of
proteins at cell surface
 Types
 Desmosomes – both
cells
 Hemidesmosomes –half

GAP JUNCTIONS
 2 membranes of cell are
connected by channel proteins
 Allow exchange of
substances/ions between cells.
 Permit transport of
substances, propogation of
electrical potential & exchange
chemical messengers.
 Examples – Heart & intestinal
mucosa.

CELL JUNCTIONS AND CYTOSKELETON

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