SynGAP isoforms exert opposing effects on synaptic strength.
Alternative promoter usage and alternative splicing enable diversification of the transcriptome. Here we demonstrate that the function of Synaptic GTPase-Activating Protein (SynGAP), a key synaptic protein, is determined by the combination of its amino-terminal sequence with its carboxy-terminal sequence. 5' rapid amplification of cDNA ends and primer extension show that different N-terminal protein sequences arise through alternative promoter usage that are regulated by synaptic activity and postnatal age. Heterogeneity in C-terminal protein sequence arises through alternative splicing. Overexpression of SynGAP α1 versus α2 C-termini-containing proteins in hippocampal neurons has opposing effects on synaptic strength, decreasing and increasing miniature excitatory synaptic currents amplitude/frequency, respectively. The magnitude of this C-terminal-dependent effect is modulated by the N-terminal peptide sequence. This is the first demonstration that activity-dependent alternative promoter usage can change the function of a synaptic protein at excitatory synapses. Furthermore, the direction and degree of synaptic modulation exerted by different protein isoforms from a single gene locus is dependent on the combination of differential promoter usage and alternative splicing.
Centre for Integrative Physiology, University of Edinburgh, Edinburgh EH8 9XD, UK.
A C
AC
McMahon
M W
MW
Barnett
T S
TS
O'Leary
P N
PN
Stoney
M O
MO
Collins
S
S
Papadia
J S
JS
Choudhary
N H
NH
Komiyama
S G N
SG
Grant
G E
GE
Hardingham
D J A
DJ
Wyllie
P C
PC
Kind
D000595:Amino Acid Sequence; D000818:Animals; D004594:Electrophysiology; D006624:Hippocampus / Q000378:metabolism; D013058:Mass Spectrometry; D051379:Mice; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D009474:Neurons / Q000201:enzymology; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D013569:Synapses / Q000378:metabolism*; D020703:ras GTPase-Activating Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
D020033:Protein Isoforms; C484512:Syngap1 protein, mouse; D020703:ras GTPase-Activating Proteins