L24 - Cytoskeleton Toxins

overview

• toxins can inhibit the formation/removal of protein subunits for protein filaments

or

• toxins can activate the formation/removal of protein subunits for protein filaments

Taxol

source: fungus living on pacific yew tree (was anti-cancerous)

mechanism:

• inhibits formation of tubulin (subunit) from MTs

consequence: cells get stuck in mitosis & CANT do metaphase or anaphase (NO cytokinesis)

significance: used to treat certain cancers - bc they CANT separate/replicate

Acrylamide

= crosslinks proteins

• synthetic + used in PAGE

• very toxic (only when its NOT cross-linked yet)

mechanism:

• activates formation of IFs to keratin (subunit)

consequence/ significance: axons are ripped to pieces on sensory neurons

• aggregates the neurofilaments

THUS, dont spill this on yourself

T6SS toxins

= assoc w gram negative bacteria + are contact dependent

• multiple toxin mechanisms

• mediates coexistence, competition, & predation defense

structure: spherical & hollow

→ friends T6SS action:

• when they have the SAME immunity proteins for survival

→ T6SS competition:

• when they DONT have the same immunity proteins (can die even if the same species)

  

Human T6SS interactions : via VgrG-1 toxin

• secretes out VgrG-1 during macrophage phagocytosis

→ destroys cell cytoskeleton machinery

note: toxin can also remain attached

mechanism:

• inhibits F-actin filament formation from G-actin

Which cytoskeleton proteins do these cytoskeleton toxins damage?

taxol : inhibits MT → tubulin (cant disassemble)

acrylamide : activates IFs → keratin (aggregates)

VgrG : inhibits F-actin by cross linking G-actin

Examinable content