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Membrane palmitoylated protein 2 is a synaptic scaffold protein required for synaptic SK2-containing channel function.

Kim G, Luján R, Schwenk J, Kelley MH, Aguado C, Watanabe M, Fakler B, Maylie J, Adelman JP - Elife (2016)

Bottom Line: We have identified a novel synaptic scaffold, MPP2 (membrane palmitoylated protein 2; p55), a member of the membrane-associated guanylate kinase (MAGUK) family that interacts with SK2-containing channels.Knocking down MPP2 expression selectively abolished the SK2-containing channel contribution to synaptic responses and decreased LTP.Thus, MPP2 is a novel synaptic scaffold that is required for proper synaptic localization and function of SK2-containing channels.

View Article: PubMed Central - PubMed

Affiliation: Vollum Institute, Oregon Health and Science University, Portland, United States.

ABSTRACT
Mouse CA1 pyramidal neurons express apamin-sensitive SK2-containing channels in the post-synaptic membrane, positioned close to NMDA-type (N-methyl-D-aspartate) glutamate receptors. Activated by synaptically evoked NMDAR-dependent Ca(2+) influx, the synaptic SK2-containing channels modulate excitatory post-synaptic responses and the induction of synaptic plasticity. In addition, their activity- and protein kinase A-dependent trafficking contributes to expression of long-term potentiation (LTP). We have identified a novel synaptic scaffold, MPP2 (membrane palmitoylated protein 2; p55), a member of the membrane-associated guanylate kinase (MAGUK) family that interacts with SK2-containing channels. MPP2 and SK2 co-immunopurified from mouse brain, and co-immunoprecipitated when they were co-expressed in HEK293 cells. MPP2 is highly expressed in the post-synaptic density of dendritic spines on CA1 pyramidal neurons. Knocking down MPP2 expression selectively abolished the SK2-containing channel contribution to synaptic responses and decreased LTP. Thus, MPP2 is a novel synaptic scaffold that is required for proper synaptic localization and function of SK2-containing channels.

No MeSH data available.


Loss of MPP2 reduces LTP.(A) Time course of the normalized EPSP amplitude (mean ± s.e.m.) from control non-fluorescent cells (ctrl, closed black symbols, n = 8) and MPP2 sh-transfected cells (MPP2, open red symbols, n = 13). The TBP protocol was delivered at time 0. Inset: representative cell showing average of 15 EPSPs taken from indicated shaded time points in ACSF (black) and 25–30 min after the induction of LTP (red); shaded areas are mean ± s.e.m. (B). Scatter plot of relative ESPS peak compared to baseline from the individual slices for non-fluorescent control (ctrl) and MPP2 sh-transfected cells. Horizontal bar reflects mean response.DOI:http://dx.doi.org/10.7554/eLife.12637.014
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fig8: Loss of MPP2 reduces LTP.(A) Time course of the normalized EPSP amplitude (mean ± s.e.m.) from control non-fluorescent cells (ctrl, closed black symbols, n = 8) and MPP2 sh-transfected cells (MPP2, open red symbols, n = 13). The TBP protocol was delivered at time 0. Inset: representative cell showing average of 15 EPSPs taken from indicated shaded time points in ACSF (black) and 25–30 min after the induction of LTP (red); shaded areas are mean ± s.e.m. (B). Scatter plot of relative ESPS peak compared to baseline from the individual slices for non-fluorescent control (ctrl) and MPP2 sh-transfected cells. Horizontal bar reflects mean response.DOI:http://dx.doi.org/10.7554/eLife.12637.014

Mentions: SK channel activity modulates the induction of synaptic plasticity (Stackman et al., 2002) and the activity-dependent endocytosis of synaptic SK2-containing channels contributes to the expression of LTP (Lin et al., 2008). To determine the consequences of MPP2 knock-down and loss of synaptic SK2-containing channel activity on LTP, a theta burst pairing protocol was delivered in which Schaffer collateral stimulations were paired with back-propagating action potentials evoked by somatic current injections. In non-transfected CA1 pyramidal neurons, this induced LTP of 407.9 ± 46.3% (n = 8), while in transfected, MPP2 knock down neurons, LTP was significantly reduced (243.0 ± 14.8%; n = 13; p<0.001) (Figure 8). Consistent with the loss of synaptic SK2-containing channels, MPP2 knock-down reduces LTP.10.7554/eLife.12637.014Figure 8.Loss of MPP2 reduces LTP.


Membrane palmitoylated protein 2 is a synaptic scaffold protein required for synaptic SK2-containing channel function.

Kim G, Luján R, Schwenk J, Kelley MH, Aguado C, Watanabe M, Fakler B, Maylie J, Adelman JP - Elife (2016)

Loss of MPP2 reduces LTP.(A) Time course of the normalized EPSP amplitude (mean ± s.e.m.) from control non-fluorescent cells (ctrl, closed black symbols, n = 8) and MPP2 sh-transfected cells (MPP2, open red symbols, n = 13). The TBP protocol was delivered at time 0. Inset: representative cell showing average of 15 EPSPs taken from indicated shaded time points in ACSF (black) and 25–30 min after the induction of LTP (red); shaded areas are mean ± s.e.m. (B). Scatter plot of relative ESPS peak compared to baseline from the individual slices for non-fluorescent control (ctrl) and MPP2 sh-transfected cells. Horizontal bar reflects mean response.DOI:http://dx.doi.org/10.7554/eLife.12637.014
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fig8: Loss of MPP2 reduces LTP.(A) Time course of the normalized EPSP amplitude (mean ± s.e.m.) from control non-fluorescent cells (ctrl, closed black symbols, n = 8) and MPP2 sh-transfected cells (MPP2, open red symbols, n = 13). The TBP protocol was delivered at time 0. Inset: representative cell showing average of 15 EPSPs taken from indicated shaded time points in ACSF (black) and 25–30 min after the induction of LTP (red); shaded areas are mean ± s.e.m. (B). Scatter plot of relative ESPS peak compared to baseline from the individual slices for non-fluorescent control (ctrl) and MPP2 sh-transfected cells. Horizontal bar reflects mean response.DOI:http://dx.doi.org/10.7554/eLife.12637.014
Mentions: SK channel activity modulates the induction of synaptic plasticity (Stackman et al., 2002) and the activity-dependent endocytosis of synaptic SK2-containing channels contributes to the expression of LTP (Lin et al., 2008). To determine the consequences of MPP2 knock-down and loss of synaptic SK2-containing channel activity on LTP, a theta burst pairing protocol was delivered in which Schaffer collateral stimulations were paired with back-propagating action potentials evoked by somatic current injections. In non-transfected CA1 pyramidal neurons, this induced LTP of 407.9 ± 46.3% (n = 8), while in transfected, MPP2 knock down neurons, LTP was significantly reduced (243.0 ± 14.8%; n = 13; p<0.001) (Figure 8). Consistent with the loss of synaptic SK2-containing channels, MPP2 knock-down reduces LTP.10.7554/eLife.12637.014Figure 8.Loss of MPP2 reduces LTP.

Bottom Line: We have identified a novel synaptic scaffold, MPP2 (membrane palmitoylated protein 2; p55), a member of the membrane-associated guanylate kinase (MAGUK) family that interacts with SK2-containing channels.Knocking down MPP2 expression selectively abolished the SK2-containing channel contribution to synaptic responses and decreased LTP.Thus, MPP2 is a novel synaptic scaffold that is required for proper synaptic localization and function of SK2-containing channels.

View Article: PubMed Central - PubMed

Affiliation: Vollum Institute, Oregon Health and Science University, Portland, United States.

ABSTRACT
Mouse CA1 pyramidal neurons express apamin-sensitive SK2-containing channels in the post-synaptic membrane, positioned close to NMDA-type (N-methyl-D-aspartate) glutamate receptors. Activated by synaptically evoked NMDAR-dependent Ca(2+) influx, the synaptic SK2-containing channels modulate excitatory post-synaptic responses and the induction of synaptic plasticity. In addition, their activity- and protein kinase A-dependent trafficking contributes to expression of long-term potentiation (LTP). We have identified a novel synaptic scaffold, MPP2 (membrane palmitoylated protein 2; p55), a member of the membrane-associated guanylate kinase (MAGUK) family that interacts with SK2-containing channels. MPP2 and SK2 co-immunopurified from mouse brain, and co-immunoprecipitated when they were co-expressed in HEK293 cells. MPP2 is highly expressed in the post-synaptic density of dendritic spines on CA1 pyramidal neurons. Knocking down MPP2 expression selectively abolished the SK2-containing channel contribution to synaptic responses and decreased LTP. Thus, MPP2 is a novel synaptic scaffold that is required for proper synaptic localization and function of SK2-containing channels.

No MeSH data available.