1

MOUVEMENT-Centriole-Centrosome-Kinetochore-Axonène-Cellule ciliée

+

+

a. Dimerization of a and b tubulin subtypes

b. Linear repitition of the heterodimers makes a

a b - a b - a b - a b - a b - a b - a b - a b - a b - a btubulin protofilament growingMicrotubule organizing

center

c. Side-by-side assembly of 13 protofilaments to make a sheet

d. Rolling of the sheet into a tubule

MICROTUBULE CONSTRUCTION

e. Elongationcontrolled by[ions] [a b ]GTP GDP rate

Colchicine blocks elongation

CB subfibersA

101013protofilaments

BUILD A CENTRIOLE or BASAL BODY

Assemble 2 partial & onecomplete microtubules intoa TRIPLET

Arrange 9 triplets in parallel &position an identical array nearby& perpendicular

CENTROSOME = 2 Centrioles +Microtubule Organizing Center

CENTRIOLES - MTOC -KINETOCHORES

2

• The cell cycle and mitosis: mechanism (example)

nonkinetochoremicrotubule

kinetochoremicrotubules

BsubfibersA

1013protofilaments

MICROTUBULES BUILD AN AXONEME of cilium or flagellum

Extend A & B subfibers to be the axoneme’s doublets

9 doublets

Other microtubule arrays arethe MITOTIC SPINDLE &AXONAL CORE

central pair

The axoneme has a 9 double MT + 2 center MT patternwith dynein arms on the outside for sliding action!

This is the “Sliding Filament Theory”

3

MICROTUBULES FOR THE CILIARY BEAT

Dynein arm with ATPaseactivity to power movement -generating a sliding interactionwith B subfiber of adjacentmicrotubule doublet

Connections turn the microtubulesliding into BENDING of the Cilium

4

MICROTUBULES FOR THE CILIARY BEAT

MEDICAL CORRELATIONSA genetic axonemal dynein deficiency impairs ciliary clearance ofthe airway, leading to severe lung infections of Kartegener’ssyndrome

Dangerous cell proliferation in cancer can be halted by vinblastinewhich blocks mitotic spindle formation

Dynein arm with ATPaseactivity to power movement -generating a sliding interactionwith B subfiber of adjacentmicrotubule doublet

Connections turn the microtubulesliding into BENDING of the Cilium

.

..

GOLGI

Zonula occludens

Zonula adherens

Macula adherens/Desmosome

Hemi-desmosome

BL

.

Keratin Intermediate Filaments

Centrioles & MTOCfor Microtubules

luminal

basal

lateral

Actin cortex

Basal bodies

CILIUM9 + 2 Microtubular array (9 doublets)

with 9 + 0 array (9 triplets)

CILIATED AIRWAY CELL

SENSORY STEREOCILIA ON AUDITORY HAIR CELL

Actin filaments

bundled, as the as thecore of the stereocilium

meshwork, as anchoringcuticular plate

Ion channelsopened bydeflection ofstereocilium

Synapses

Stereocilia arenon-motile,but can bemoved by thestimulus

SENSORY STEREOCILIA ON AUDITORY HAIR CELL

Actin filamentscore of the stereocilium

meshwork

Stereocilia arenon-motile,but can bemoved by thestimulus

Hair cell alsohas a solitarytall truecilium, withmicrotubules

5

SENSORY STEREOCILIA ON AUDITORY HAIR CELL

Actin filaments

bundled, as the as thecore of the stereocilium

Ion channels

Synapses

meshwork

& Stereociliaare non-motile

Note: nomicrotubules in thesignal-transductionmechanism

So why the‘cilium’ name?

Why, indeed!

Dynein arms move acrossadjacent MTs and cause

sliding and axonemalbendingmotion

6

CELL SHAPES

1 Cylindrical/columnar, cuboidal, polyhedral, flattened epithelial cell shapes to fit into multicellular patterns

2 Spheroid & Ovoid - defensive blood cells

3 Elongated - muscle cells & fibroblasts

4 Multiple branching processes - neurons, glial cells, pigment cells

Generalization

Microtubules and intermediate filaments with cell junctionshold shape and polarization

Actin microfilaments (with & without myosin) modify shape

VARIETIES OF MOVEMENT

Ciliary & Flagellar

Intracellular vesicles

Chromatids during mitosis

Whole cell (sperm)

by MICROTUBULES

Whole cell

Extension of processes

Separation of cells at mitosis

Intracellular vesicles

by ACTIN FILAMENTS

GeneralizationsLittle direct motor role for Intermediate FilamentsMicrotubules & IFs highly concentrated around the nucleus &extend radially; actin more peripheral under the plasmalemma inthe “cortex” Exceptions are: muscle, neurons, mature epidermal cells, RBCs

Movements are closely related to cell’s shape & polarity