memory maintenance Flashcards
how should memories be maintained
biochemical trace needs to be maintained
how can biochemical trace be maintained (4)
- persistent protein kinases retain phosphorylation of synaptic proteins
- insertion of membrane proteins (like AMPAR) maintained
- structural changes (size of synapse) may be long-lasting
- new synapses
what process may be required for memory erasure
AMPAR endocytosis
structure of protein kinases (like PKA) in inactive state
- 2 domains: regulatory & catalytic
- binding of pseudosubstrate keeps both domains linked together -> inactive
- pseudosubstrate stops kinase from phosphorylating things
which domain makes protein kinases inactive
regulatory domain
structure of protein kinases (like PKA) in active state (3)
- 2nd messenger binds to regulatory domain -> causes conformational change
- regulatory and catalytic domains no longer linked -> active
- catalytic domain can phosphorylate things
role of anchoring proteins that bind to protein kinases
bring the protein kinase to appropriate substrate
how does PKA become persistently active
regulatory domain ubiquitinated and targeted for proteolysis
structure of PKA, how becomes active and persistent activity
- separate regulatory and catalytic subunits
- cAMP binding causes dissociation of subunits
- timing to re-bind is important
- degradation of regulatory subunit leads to persistent activity of PKA and leaves molecular memory trace
how test for induction of memory trace
inhibiting process (kinase) before or during experience tests
how test for mechanisms involved in maintaining trace
inhibiting process (kinase) after experience
effect of inhibiting PKA (during stimulation with 5HT)
- removes increase in synaptic strength (LTF) for 12 hours after stimulation
- after 12h, no more effect of inhibitor
what did experiment inhibiting PKA lead to conclude
that mechanism for memory maintenance changes bw 12 and 24 h
what is camkii and how is it activated
- kinase activated by calcium influx
- dodecamer
- calcium binds to calmodulin and both bind kinase and activate it
how does camkii become constitutively active
phosphorylation by neighboring subunit (autophosphorylation) -> cascade of phosphorylation
limits to persistent activation of camkii (2)
- critical site cannot be rephosphorylated in absence of calmodulin (calcium-camodulin acting as substrate (bound) is required)
- after end of stimulation, phosphatases remove phosphates on subunits -> inactivation
technique to measure camkii activation in-situ + explain (4)
- FRET -> measure distance bw 2 fluorophores
- add fluorophore to kinase -> activation of kinase changes distance
- inactive camkii -> fluorophores close together so red emission (FRET transfer of energy)
- active camkii -> confo change, fluorophores far from eo so no energy transfer
results of measure camkii activation with fret (4)
- camkii is transiently activated
- becomes inactie after 1 min
- however, spine got bigger (sign of LTP)
- camkii important for induction of memory, but not for maintenance of memory
what is camkii important for
induction of memory
other than autophosphorylation, what other way can camkii be persistently activated
directly binding to NMDARs that lock it into an active state
effect of losing interaction bw camkii and NMDARs (3)
- only minor learning impairments
- LTP induction inhibited
- maintenance not affected
adding camkii inhibitor (a) before inducing ltp, (b) after inducing ltp
before: blocks ltp (memory induction)
after: does nothing (memory still maintained)
what causes persistent activation of pkc
loss of regulator domain (similar to pka)
difference bw pkc and pka structure (2)
pkc: regulatory and catalytic domain on same molecule (~ camkii) + no phosphorylation site that leads to persistent activation