L4 - Microtubule motors in vesicle transport Flashcards
(22 cards)
what are microtubules
long polymers made of alpha and beta tubulin
= anchored at centrosome in centre of cell and polymerise outwards
what do microtubules contain - 2 things
- alpha and beta tubular
- Positive and negative end
= acts as molcular scaffold and transport molceules through cell
which end is rapildy polymerised in microtubules
+ end
= reaches out to periphery/edges
which dirtection along microtubules do kinesins move material
Towards + end
= centrosome to periphery
which direction do dyneins move material along microtubules
towards - end
= periphery to centrosome
name rthe 3 cytokeletal motors and where they work
Kinesisns = microtubules –> positive end
Dyneins = microtubules –> negative ends
Myosins = actin cytoskeleton
name the 3 common domains in cytokeletal motors
Cargo binding
Linker region
Cytoskeletal binding/mtor domain
describe how kinesins/dyneins move simply
- motor domains bind to cytokeleton/Microtubule
- ATP hydrolysed for energy –> directional movement
= cargo domains are ascociated with specific cargo
what happenes when microtubules or one of the mahor motor proteins are disrupted
Golgi is scattered
= Microtubules are scaffolds –> inhibitor of MTs = golgi falls apart
decsribe a property of the movement of vesicles along cytoskeleton
bi-directional
= depending on which motors vesicles are asociated with
why is bit hard to determine bwhich sepecific motor types are responsible for specific transport pathwats
redundancy
= Many motor proteins can perform similar tasks
= one motor inhibited another may compensate
what is a PX domain
bind to membrane lipids
= preference for 3’ phosphorlated lipids
= P13P
describe the structure of Kif16B
kinesin
- motor domain
- PX domain –> lipid binding
- coiled-coil domain –> dimerisation/form of functional motor
where is PI3P concentrated and why is this important in terms of Kif16B
PX domain of Kif16B has very high affinity for PI3P
= part of the way the motor recognises cargo is by phospholipid content of membrane
= PI3P concentrated on endosomal and post-golgi compartments
what do Kif16B knockout tissyes fail to form in embryogeneis
primitive ectoderm –> only forms Inner cell mass
= FGF signalling impaired –> growth factor
what is ectoderm differentiation controlled by
FGF signalling –> growth factor
= FGF binds to receptor activating Akt/Erk kinases
= important in P13 pathway + cell cycle/proliferation
what happenes in KIF16B knockout tissues that prevents TGF signalling
FGFR not trafficked to the membrane
= no signalling with FGF growth factor
name the GTPase protein that was founf to inetract with Kif16B
Rab14
= interacting domain overalps PX domain
= coincidence detection –> specificity is protein-lipid AND protein-protein
define coincidience detection
protein only becomes active when two or more signals are present at the same time
= prevents accidental activation when only one signal is present
= security system that requires both a fingerprint and a password—it won’t unlock unless both are correct!
what would knocoking out a Rab proteins ability to bind nucletide cause
dominant negative
= always inactive = cannot swap inactive GDP for active GTP
how can we use dominant negative Rab14 to analyse Kif16B pathway
- use a mutant Rab14 that blocks Rab14 function
- Compare it to KIF16B knockout embryos
Finding:
The Rab14 mutant causes the same defects as the KIF16B knockout
= suggests Rab14 and KIF16B work in the same pathway for early development.
= When either is broken (mutant Rab14 or missing KIF16B) –> development fails the same way.
what does Kif16B/kinesin bind to when GTP bound
Rab14 + FGF receptor vesicles
= knockout of either the motor or the Rab impairs deleivery of FGFR to membrane
= No FGF signalling –> No embryo ectoderm development
