cytoskeleton

1) ACTIN MICROFILAMENTS

2) INTERMEDIATE FILAMENTS – less dynamic than actin and microtubules

3) MICROTUBULES

*only eukaryotes, 3d structure that fills cytoplasm

Toughest can withstand the most stress w/o breaking because they are constructed from subunits like a rope

**IF network can survive death of cells *hair, fur, nails, outer covering of skin

Mechanical stability to the whole cell for cytoplasmic intermediate filaments and nuclear envelope to nuclear IF

Keratine – epithelia

Vimentin and vimentin related – connective tissue, muscle cells, and glial cells

Neurofilaments – nerve cells

Nuclear lamins – all animal cells (all cell types contain nuclear lamin)

The spread of a disease process from one part of the body to another, as in the appearance of neoplasms in parts of the body remote from the site of the original tumor; results  from the dissemination of tumor cells  by the lymphatics or blood vessels or by direct extension through serous (body) cavities)

• This is used    extensively by pathologists for       characterizing the     tissue  of   origin   of a tumor celL that may have metastasized  
• Unlike the actin and tubulin isoforms, IF protein classes are widely divergent in sequence
• Can biopsy a tumor from any location and test for the type of IF it contains-in this way, can determine in what tissue type the tumor       originated Cell/tissue type of origin influences treatment of tumor

Line inside of the nuclear enevelope and give mechanical strength to nuclear membrane

**only cytoskeleton filaments that are not cytoplasmic

Found in all human cells

50% of actin aubunits are assembled into filaments, other is free

Subunits rapidly cycle back and forth between being free and then assembled

Its composed of a 2 stranded helix with plus end and minus end, the subunits add on the plus end and fall of at the minus end. G actin unassembled globular actin monomers while F actin assemble actin filaments

**because actin is abundant, when polymerizes it can push out plasma membrane to change shape of the whole cell within seconds, the way it is polymerized inside the cell is the determination of cell shape, can occur at the same time in the same cell

Cell motility

Contraction

Determine shape of cells surface

Absorption

Secretion

Cellular adhesion

Mechanitransduction

Needed for lots of transporters (intrinsic membrane proteins with transmembrane domains) to take up ingested materials

Cross links

Severs

Nucleates actin to form a different structure

**actin can form so many structure due to large number of ABP

An active Motor protein that depend on the interaction of myosin with actin that can slide one actin filament past another or moves cargo such as vesicles along actin filaments using ATP as fuel

Forming from actin polymerization crawling pushes the cell forward to create this formation

All human cells

Are heterodimers of A and B tubulin

Tubulin heterodimers rapidly cycle back and forth between being free and assembled which when assembled form a hollow microtubule

Determine position of intracellular organelles and provide tracks for intracellular transport for components such as vesicles and organelles with motors

Form cilia and flagella and mitotic spindle

Assisted in functions by microtubule associated proteins

Kinesin-transport materials toward + end

Dynein – transports material toward – end

Motile by projections from cell surface that are made up of MT and covered by extension of PM and designed to move cell itself or to move substances like mucus or extracellular fluid overlying the ciliated cells

Nucleated by basal body (like a centrosome)

Microtubules in cilium or flagellum are arranged in a 9+2 array (used to recognize MTs on Ems)

Flagella longer than cilia

Both grow out of MTs in a centriole basal body with same 9 triplet of MT structure

Cell have multiple cilia but one flagellum

Only cell in human body that has one is spem

Found in respiratory tract (drive debris out of lung) fallopian tubes (drive egg from ovary)

Assembly gives a + and a – end. They grow and shrink by add and loss of tubulin heterodimers at + end inside the cell. Tubulin heterodimers add on GTP form and fall of GDP form

Inside of the cell, grow out of a structure centrosomes composed of 2 centrioles surrounded by cloud of proteins called pericentriolar material (cell division)

Located on one side of nucleus under golgi stacks

**motc caps minus end of MT and + end grows out to periphery

Is a component of the pericentriolar material of MT

It nucleates or provides start for MT to grow hundreds from 1 centrosome

MT grows and shrinks independently of its neighbors

Motor for beating of cilia and flagella that slides one MT doublet past another bends cilium or flagellum by using ATP

Genetic disorder of cellular cilia. Have overlapping clinical features in multiple organs because cilia function in many diff tissues

Rare autosome recessive genetic disorder that causes lack of axonemal dynein in motile cilia (action of cilia lining) i.e fallopian tube, respiratory tract

Reduced of absent mucus clearance from lungs leading to susceptibility to chronic respiratory infections

Infertility resulting from immotile sperm

MT disassemble from interphase conformation and reassemble to form mitotic spindle, centrosome double in dividing cells prior to mitosis, plus ends of MT plug into kinetochores on chromosome and the MT pull sister chromatids apart into 2 daughter cell

Anti cancer drugs – MT specific drugs are important because if you inhibit MTs ability to form the mitotic spindle you inhibit cell division

Treatment for gout

Taxol – binds and stabilizes microtubules

Colchicine, colcemid – binds and subunits and prevents their polymerization

Vinblastine, vincristine – binds subunits and prevents their polymerization

Nocodazole - binds subunits and prevents their polymerization

Actin and MT-actin forms lamellipodium to cell crawl. Actin pulls cells forward while MT guide direction of growth. Inhibit MT function, you can inhibit cell crawling

Formation of uric acid crystals in joints

Painful swelling and attracts leukocytes that amplify the inflammation

Prescribed for acute attacks at low levels for prevention of gout

By inhibiting functions MT, colchicine prevents the migration of leukocytes to the region and thereby reduces the associated inflammation of gout

Cadherins (1st type of cell adhesion molecule) transmembrane proteins

Adhere one cell to another in a calcium dependent fashion

**calcium concentration doesn’t regulate binding cause calcium in always high in extracellular fluid

Junction between 2 cells that contain cadherins and link to tough IF (i.e. tissue layers)

Rare autoimmune disease that form group of blistering (“” vulgaris is common type)

Autoantibodies form against a component of desmosome which normally holds skin together.

Auto antibodies attack and destroy desmosomes skin separates from each other and becomes unglued causing blisters that slough off and turn into sores

Transmembrane heterodimeric proteins that constitute the main receptors for extracellular matrix components

Sense whether adhesion can occur

Link to cytoskeleton on inside of cell (actins of IF)

**many types exist, one cell can have multiple types of surface

Before ligand binding, intergrins activate signal transduction pathway that mediate cellular signals such as reg of cell cycle, organization of intracellular cytoskeleton, and movement of new receptors to the cell membrane

Activated by binding of ECM and cytoskeleton causes conformational change in integrins (inactive if no binding)

 

When activated, integrins trigger signal transduction, informing the cell of chemical composition and mechanical status of ECM. This allows for rapid and flexible responses to events on cell surface (can activate in lipid rafts)