Croom Flashcards
size (length) of neuropeptides?
neuropeptides range from about 10-100 amino acids in length
Biosynthesis of Neuropeptide
Stages of neuropeptide synthesis and refinement:
1. prepropeptide
made by ribosomes, sent to the ER for cleavage
2. propeptide
made in ER by signal peptidase, sent to Golgi
3. peptide
further cleaved and packed into dense core vesicles
Neuropeptides may undergo further post-translational modifications before they are
fully functional!
○ Ribosome in soma makes prepropeptide
○ Cleaved to propeptide in ER
○ Cleaved to peptide & packed in Golgi
○ Sent to synaptic bouton via DCV (undergoes post-translational mods along the way)
signal sequence sends
prepropeptide to the ER
● cleavages carried out by
Ca2+-dependent endoproteases
PC1 and PC2, which are
expressed only in neurons and
endocrine cells
● Endopeptidases cleave only at
Lys-Lys, Lys-Arg, Arg-Lys, and
Arg-Arg sites
● neuropeptides do NOT undergo
local synthesis!
Neuropeptide Packaging
● Occurs at the level of the Golgi
● Smaller DCVs may bud off from the Golgi and
then undergo homotypic fusion to form a larger
DCV
● One DCV may contain multiple types of cargo
● Endosome-associated recycling protein (EARP)
complex is required for cargo packaging
○ A pool of EARP subunits resides near the trans-golgi
network to be available for DCV packaging
diameter of a synaptic vesicle is 40nm
diameter of a DCV is 75-100nm
Neuropeptide Release
● DCVs fuse with the plasma
membrane○ Do not need to be that close to Ca2+
channels - rely more on intracellular
Ca2+ stores
○ Very similar to synaptic vesicle
docking - different proteins with
analogous functions
○ Example: calcium-activated protein
for secretion (CAPS) instead of
synaptotagmin
● Neuropeptides are NOT
reuptaken the way
neurotransmitters are - they are
used once and then discarded
● Components of the DCV itself will
be reintegrated into presynaptic
cell○ Can be either discarded or returned
to soma and reused
Some NPs and what they modulate
● Dynorphin: synapse modulation
● Substance P: pain mediation
● CCK, NPY, etc: feeding behavior
● Vasopressin: blood salinity regulation
● Oxytocin: reproductive behaviors
● Cone snail venoms: toxicity! paralysis!
