Category:Synaptic Plasticity - Revision history

Bradley Monk: /* FOOTNOTES */

2015-01-07T10:56:25Z

FOOTNOTES

← Older revision		Revision as of 03:56, 7 January 2015
Line 391:		Line 391:

	==FOOTNOTES==		==FOOTNOTES==

			{{ExpandBox\|width=80%\|float=left\|opener=View\|EXPAND TO VIEW FOOTNOTES\|

	* [i] Expression of a protein on a null background involves using CRE to selectively excise genes that have been previously flanked by LoxP sites. In this case genes coding for GluA1-3 were removed by CRE, resulting in the complete absence of AMPARs. On this AMPAR-null background, mutant GluR can then be expressed to isolate effects limited to a single subunit. The term overexpression refers to a method where virus or biolistic transfection is used to insert an extra copy of some gene on a wild-type background (one where the endogenous gene is left intact); since there are now two (or more) copies of that gene encoding for a single type of protein, overexpressed genes often result in overexpressed proteins compared to the wild-type.		* [i] Expression of a protein on a null background involves using CRE to selectively excise genes that have been previously flanked by LoxP sites. In this case genes coding for GluA1-3 were removed by CRE, resulting in the complete absence of AMPARs. On this AMPAR-null background, mutant GluR can then be expressed to isolate effects limited to a single subunit. The term overexpression refers to a method where virus or biolistic transfection is used to insert an extra copy of some gene on a wild-type background (one where the endogenous gene is left intact); since there are now two (or more) copies of that gene encoding for a single type of protein, overexpressed genes often result in overexpressed proteins compared to the wild-type.
	* [ii] Interestingly, despite it’s significantly reduced surface expression, GluR1ΔC rescued EPSCs to the same degree as full-length GluR1.		* [ii] Interestingly, despite it’s significantly reduced surface expression, GluR1ΔC rescued EPSCs to the same degree as full-length GluR1.
Line 401:		Line 404:
	* [ix] (1) whether it has a bound nucleotide, and if so, which of three hydrolysis states [adenosine triphosphate (ATP), adenosine diphosphate (ADP), or ADP with bound inorganic phosphate (Pi)] that nucleotide is in, (2) which end of the filament it is associating with or dissociating from, (3) the state of the bound nucleotide of the existing filament end (and possibly deeper into the filament as well), (4) the age of the filament,2 (5) what binding proteins are associated with the actin monomer, (6) what binding or bundling proteins are associated with the filament, and finally (7) the magnitude of a force exerted on the filament (Bindschadler 2010).		* [ix] (1) whether it has a bound nucleotide, and if so, which of three hydrolysis states [adenosine triphosphate (ATP), adenosine diphosphate (ADP), or ADP with bound inorganic phosphate (Pi)] that nucleotide is in, (2) which end of the filament it is associating with or dissociating from, (3) the state of the bound nucleotide of the existing filament end (and possibly deeper into the filament as well), (4) the age of the filament,2 (5) what binding proteins are associated with the actin monomer, (6) what binding or bundling proteins are associated with the filament, and finally (7) the magnitude of a force exerted on the filament (Bindschadler 2010).
	* [x] This is in contrast to representing probabilistic forces solely as geometric fields. Probabilistic/stochastic processes can be assigned to a defined spatial region (e.g. SAP binding) without the need to render individual particles; but this convention precludes asking questions about particle turnover (e.g. what percent of the original SAP particles remain after 24 hours?). [I’m not 100% certain about the accuracy of the previous statement - it seems logical but still need to confirm with Danny or better yet Shouval or Holcman].		* [x] This is in contrast to representing probabilistic forces solely as geometric fields. Probabilistic/stochastic processes can be assigned to a defined spatial region (e.g. SAP binding) without the need to render individual particles; but this convention precludes asking questions about particle turnover (e.g. what percent of the original SAP particles remain after 24 hours?). [I’m not 100% certain about the accuracy of the previous statement - it seems logical but still need to confirm with Danny or better yet Shouval or Holcman].
			}}

Bradley Monk: /* REFERENCES */

2015-01-07T10:55:35Z

REFERENCES

← Older revision		Revision as of 03:55, 7 January 2015
Line 224:		Line 224:

	==REFERENCES==		==REFERENCES==

			{{ExpandBox\|width=80%\|float=left\|opener=View\|EXPAND TO VIEW BIBLIOGRAPHY\|

	* 1. Bristol, U.o. in Neural pathways (2014).		* 1. Bristol, U.o. in Neural pathways (2014).
	* 2. Rodgriguez, P.R. (ed. Tutorial, A.I.) (Sinaur Associates Inc. & Sumanas Inc, Neuroscience 4th Ed., 2008).		* 2. Rodgriguez, P.R. (ed. Tutorial, A.I.) (Sinaur Associates Inc. & Sumanas Inc, Neuroscience 4th Ed., 2008).
Line 381:		Line 384:
	* 156. Hoze, N. et al. Heterogeneity of AMPA receptor trafficking and molecular interactions revealed by superresolution analysis of live cell imaging. Proc Natl Acad Sci U S A 109, 17052-7 (2012).		* 156. Hoze, N. et al. Heterogeneity of AMPA receptor trafficking and molecular interactions revealed by superresolution analysis of live cell imaging. Proc Natl Acad Sci U S A 109, 17052-7 (2012).
	* 157. Renner, M., Choquet, D. & Triller, A. Control of the postsynaptic membrane viscosity. J Neurosci 29, 2926-37 (2009).		* 157. Renner, M., Choquet, D. & Triller, A. Control of the postsynaptic membrane viscosity. J Neurosci 29, 2926-37 (2009).
			}}

	==Wiki References==		==Wiki References==

Bradley Monk: /* DO CTAILS OR TARPS REGULATE AMPAR TRAFFICKING? */

2015-01-07T10:54:28Z

DO CTAILS OR TARPS REGULATE AMPAR TRAFFICKING?

← Older revision		Revision as of 03:54, 7 January 2015
Line 114:		Line 114:


			==Surface Diffusion==


			{{Style\|class=div\|size=12px\|border=1px dotted red\|font=Courier\|background=#F8F8F8\|pad=1px\|margin=1px\|width=50%;\|
			<syntaxhighlight lang="matlab" line start="1" highlight="0" enclose="div">
			%-------------###############################----------------%
			% Two Dimensional Realistic Brownian Motion
			%-------------###############################----------------%

			dimensions = 2; % two dimensional simulation
			tau = .1; % time interval in seconds
			time = tau * 1:N; % create a time vector for plotting

			k = sqrt(D * dimensions * tau);
			dx = k * randn(N,1);
			dy = k * randn(N,1);

			x = cumsum(dx);
			y = cumsum(dy);

			dSquaredDisplacement = (dx .^ 2) + (dy .^ 2);
			squaredDisplacement = ( x .^ 2) + ( y .^ 2);

			plot(x,y);
			title('Particle Track of a Single Simulated Particle');

			%-------------############################------------------%
			</syntaxhighlight>
			}}



			{{Style\|class=div\|size=12px\|border=1px dotted red\|font=Courier\|background=#F8F8F8\|pad=1px\|margin=1px\|width=50%;\|
			<syntaxhighlight lang="matlab" line start="1" highlight="0" enclose="div">
			clc; close all; clear all;
			%===================================%
			% STARTING PARAMETERS
			%-----------------------------------%

			Ndots = 200; % number of particles in ES
			NSteps = 500; % number of steps per trial

			Sc = 1.0; % scale of model
			dT = 0.1; % time step (s)
			m = 2; % spatial dimensions

			Des = (ScdT) .13; % D coef ES
			Dsb = (ScdT) .05; % D coef Syn Basal
			Dsp = (ScdT) .01; % D coef Syn LTP

			k = sqrt(m*Des); % sd of Des step-size distribution

			XYL = zeros(2,Ndots); % XY particle locations
			XYS = zeros(2,Ndots); % XY particle step sizes
			XYLp = zeros(2,NSteps); % preallocate matrix for trace dot

			DendSz = [3 6] ./Sc; % surface area (µm) scaled
			SIZE.x = DendSz(1)/2; % half enclosure size X-dim
			SIZE.y = DendSz(2)/2; % half enclosure size Y-dim



			%===================================%
			% FIGURE SETUP
			%-----------------------------------%

			Flh = figure(1);
			[Flh] = FIG1FORMAT(Flh, SIZE);

			Ph1 = scatter(XYL(1,:),XYL(2,:),5,[0 0 1]);
			[Ph1] = PLOT1FORMAT(Ph1, SIZE);


			%===================================%
			% MAIN LOOP
			%-----------------------------------%
			for Nt = 1:NSteps

			% generates step sizes
			XYS = (k * randn(2,Ndots));

			% adds step to location
			XYL = XYL+XYS;

			% rebound at enclosure walls
			[XYL] = ENCLOSE(Nt,XYL,SIZE.x,SIZE.y,Ndots);

			% save step of first dot (for trace)
			XYLp(:,Nt) = XYL(:,1);

			% plot diffusion
			TracePlot(Nt,XYL,Ph1,XYLp,1)

			end %[for loop]
			%===================================%

			</syntaxhighlight>
			}}




			----
	<br>		<br>
	{{Clear}}		{{Clear}}

Bradley Monk at 05:34, 2 January 2015

2015-01-02T05:34:22Z

← Older revision		Revision as of 22:34, 1 January 2015
Line 110:		Line 110:

	What would multivalency mean in the context of LTP? Perhaps this is a key property that makes endogenous LTP possible. In the Malinow model, GluR2 populates basal synapses and LTP elicits GluR1 synaptic influx; given that [[Lu_Nicoll_2009#Fig_6\|GluR1/2 heteromers compose over 80% of the AMPARs on the surface]]		What would multivalency mean in the context of LTP? Perhaps this is a key property that makes endogenous LTP possible. In the Malinow model, GluR2 populates basal synapses and LTP elicits GluR1 synaptic influx; given that [[Lu_Nicoll_2009#Fig_6\|GluR1/2 heteromers compose over 80% of the AMPARs on the surface]]
	<ref name="Lu_Nicoll_2009">[[Lu_Nicoll_2009#Fig_6\|59]]~~, text~~</ref>.		<ref name="Lu_Nicoll_2009">[[Lu_Nicoll_2009#Fig_6\|59]]</ref>.

Bradley Monk at 05:32, 2 January 2015

2015-01-02T05:32:43Z

← Older revision		Revision as of 22:32, 1 January 2015
Line 109:		Line 109:
	three features emerge from consideration of the supramolecular assemblies that might promote multivalent interactions (Fig. 1). First, although the exact stoichiometry of TARP per AMPAR remains unclear, and may vary depending on cell type9–12, recent models of hippocampal neurons suggest the presence of either two or four units per receptor11. Hence, synaptic TARP-containing AMPAR complexes would present two or more identical PDZ domain–binding motifs from the auxiliary subunits. Second, postsynaptic MAGUKs, which are key elements of the PSD architecture13, share the same domain topology and in particular include a repeat of three clustered class I PDZ domains14,15 that provide anchoring sites for multiple binding partners13. Furthermore, the relative orientation of the ligand-binding grooves of the first two PDZ domains of PSD-95 favors accommodating multiple ligands originating from the same face, according to a NMR-derived structural model16. Functional studies in neurons indicate that the AMPAR–Stargazin complex preferentially binds to either or both of the first two PSD-95 PDZ domains4,17. Finally, the oligomerization properties of MAGUKs add another degree of complexity that allows for multivalent interactions. In particular, PSD-95α (predominant in neurons18) can form dimeric or multimeric assemblies via the N-terminal region17. Notably, this property is critical for the AMPAR’s synaptic function, as mutants that prevent oligomerization show effects on basal AMPAR currents4,17.		three features emerge from consideration of the supramolecular assemblies that might promote multivalent interactions (Fig. 1). First, although the exact stoichiometry of TARP per AMPAR remains unclear, and may vary depending on cell type9–12, recent models of hippocampal neurons suggest the presence of either two or four units per receptor11. Hence, synaptic TARP-containing AMPAR complexes would present two or more identical PDZ domain–binding motifs from the auxiliary subunits. Second, postsynaptic MAGUKs, which are key elements of the PSD architecture13, share the same domain topology and in particular include a repeat of three clustered class I PDZ domains14,15 that provide anchoring sites for multiple binding partners13. Furthermore, the relative orientation of the ligand-binding grooves of the first two PDZ domains of PSD-95 favors accommodating multiple ligands originating from the same face, according to a NMR-derived structural model16. Functional studies in neurons indicate that the AMPAR–Stargazin complex preferentially binds to either or both of the first two PSD-95 PDZ domains4,17. Finally, the oligomerization properties of MAGUKs add another degree of complexity that allows for multivalent interactions. In particular, PSD-95α (predominant in neurons18) can form dimeric or multimeric assemblies via the N-terminal region17. Notably, this property is critical for the AMPAR’s synaptic function, as mutants that prevent oligomerization show effects on basal AMPAR currents4,17.

	What would multivalency mean in the context of LTP? Perhaps this is a key property that makes endogenous LTP possible. In the Malinow model, GluR2 populates basal synapses and LTP elicits GluR1 synaptic influx; given that [[Lu_Nicoll_2009#Fig_6\|GluR1/2 heteromers compose over 80% of the AMPARs on the surface]] <ref name="~~Lu Nicoll 2009~~" />[[Lu_Nicoll_2009#Fig_6\|59]] text</ref>.		What would multivalency mean in the context of LTP? Perhaps this is a key property that makes endogenous LTP possible. In the Malinow model, GluR2 populates basal synapses and LTP elicits GluR1 synaptic influx; given that [[Lu_Nicoll_2009#Fig_6\|GluR1/2 heteromers compose over 80% of the AMPARs on the surface]]
			<ref name="Lu_Nicoll_2009">[[Lu_Nicoll_2009#Fig_6\|59]], text</ref>.

Bradley Monk at 05:29, 2 January 2015

2015-01-02T05:29:11Z

← Older revision		Revision as of 22:29, 1 January 2015
Line 109:		Line 109:
	three features emerge from consideration of the supramolecular assemblies that might promote multivalent interactions (Fig. 1). First, although the exact stoichiometry of TARP per AMPAR remains unclear, and may vary depending on cell type9–12, recent models of hippocampal neurons suggest the presence of either two or four units per receptor11. Hence, synaptic TARP-containing AMPAR complexes would present two or more identical PDZ domain–binding motifs from the auxiliary subunits. Second, postsynaptic MAGUKs, which are key elements of the PSD architecture13, share the same domain topology and in particular include a repeat of three clustered class I PDZ domains14,15 that provide anchoring sites for multiple binding partners13. Furthermore, the relative orientation of the ligand-binding grooves of the first two PDZ domains of PSD-95 favors accommodating multiple ligands originating from the same face, according to a NMR-derived structural model16. Functional studies in neurons indicate that the AMPAR–Stargazin complex preferentially binds to either or both of the first two PSD-95 PDZ domains4,17. Finally, the oligomerization properties of MAGUKs add another degree of complexity that allows for multivalent interactions. In particular, PSD-95α (predominant in neurons18) can form dimeric or multimeric assemblies via the N-terminal region17. Notably, this property is critical for the AMPAR’s synaptic function, as mutants that prevent oligomerization show effects on basal AMPAR currents4,17.		three features emerge from consideration of the supramolecular assemblies that might promote multivalent interactions (Fig. 1). First, although the exact stoichiometry of TARP per AMPAR remains unclear, and may vary depending on cell type9–12, recent models of hippocampal neurons suggest the presence of either two or four units per receptor11. Hence, synaptic TARP-containing AMPAR complexes would present two or more identical PDZ domain–binding motifs from the auxiliary subunits. Second, postsynaptic MAGUKs, which are key elements of the PSD architecture13, share the same domain topology and in particular include a repeat of three clustered class I PDZ domains14,15 that provide anchoring sites for multiple binding partners13. Furthermore, the relative orientation of the ligand-binding grooves of the first two PDZ domains of PSD-95 favors accommodating multiple ligands originating from the same face, according to a NMR-derived structural model16. Functional studies in neurons indicate that the AMPAR–Stargazin complex preferentially binds to either or both of the first two PSD-95 PDZ domains4,17. Finally, the oligomerization properties of MAGUKs add another degree of complexity that allows for multivalent interactions. In particular, PSD-95α (predominant in neurons18) can form dimeric or multimeric assemblies via the N-terminal region17. Notably, this property is critical for the AMPAR’s synaptic function, as mutants that prevent oligomerization show effects on basal AMPAR currents4,17.

	What would multivalency mean in the context of LTP? Perhaps this is a key property that makes endogenous LTP possible. In the Malinow model, GluR2 populates basal synapses and LTP elicits GluR1 synaptic influx; given that [[Lu_Nicoll_2009#Fig_6\|GluR1/2 heteromers compose over 80% of the AMPARs on the surface]] <ref name=~~Lu_Nicoll_2009~~/>[[Lu_Nicoll_2009#Fig_6\|59]]</ref>.		What would multivalency mean in the context of LTP? Perhaps this is a key property that makes endogenous LTP possible. In the Malinow model, GluR2 populates basal synapses and LTP elicits GluR1 synaptic influx; given that [[Lu_Nicoll_2009#Fig_6\|GluR1/2 heteromers compose over 80% of the AMPARs on the surface]] <ref name="Lu Nicoll 2009" />[[Lu_Nicoll_2009#Fig_6\|59]] text</ref>.


Line 116:		Line 116:






	~~http://www.bradleymonk.com/Lu_Nicoll_2009#Fig_6~~


Line 289:		Line 284:

	==Wiki References==		==Wiki References==
	<references/>		<references />
	~~<ref name=Lu Nicoll 2009/>TextHere</ref> <ref>Lu Nicoll 2009</ref>~~

	==FOOTNOTES==		==FOOTNOTES==
Line 303:		Line 298:
	* [ix] (1) whether it has a bound nucleotide, and if so, which of three hydrolysis states [adenosine triphosphate (ATP), adenosine diphosphate (ADP), or ADP with bound inorganic phosphate (Pi)] that nucleotide is in, (2) which end of the filament it is associating with or dissociating from, (3) the state of the bound nucleotide of the existing filament end (and possibly deeper into the filament as well), (4) the age of the filament,2 (5) what binding proteins are associated with the actin monomer, (6) what binding or bundling proteins are associated with the filament, and finally (7) the magnitude of a force exerted on the filament (Bindschadler 2010).		* [ix] (1) whether it has a bound nucleotide, and if so, which of three hydrolysis states [adenosine triphosphate (ATP), adenosine diphosphate (ADP), or ADP with bound inorganic phosphate (Pi)] that nucleotide is in, (2) which end of the filament it is associating with or dissociating from, (3) the state of the bound nucleotide of the existing filament end (and possibly deeper into the filament as well), (4) the age of the filament,2 (5) what binding proteins are associated with the actin monomer, (6) what binding or bundling proteins are associated with the filament, and finally (7) the magnitude of a force exerted on the filament (Bindschadler 2010).
	* [x] This is in contrast to representing probabilistic forces solely as geometric fields. Probabilistic/stochastic processes can be assigned to a defined spatial region (e.g. SAP binding) without the need to render individual particles; but this convention precludes asking questions about particle turnover (e.g. what percent of the original SAP particles remain after 24 hours?). [I’m not 100% certain about the accuracy of the previous statement - it seems logical but still need to confirm with Danny or better yet Shouval or Holcman].		* [x] This is in contrast to representing probabilistic forces solely as geometric fields. Probabilistic/stochastic processes can be assigned to a defined spatial region (e.g. SAP binding) without the need to render individual particles; but this convention precludes asking questions about particle turnover (e.g. what percent of the original SAP particles remain after 24 hours?). [I’m not 100% certain about the accuracy of the previous statement - it seems logical but still need to confirm with Danny or better yet Shouval or Holcman].
	*

Bradley Monk: /* REFERENCES */

2015-01-02T05:24:28Z

REFERENCES

← Older revision		Revision as of 22:24, 1 January 2015
Line 288:		Line 288:
	* 157. Renner, M., Choquet, D. & Triller, A. Control of the postsynaptic membrane viscosity. J Neurosci 29, 2926-37 (2009).		* 157. Renner, M., Choquet, D. & Triller, A. Control of the postsynaptic membrane viscosity. J Neurosci 29, 2926-37 (2009).

	==Wiki References]]		==Wiki References==
	<references/>		<references/>
			<ref name=Lu Nicoll 2009/>TextHere</ref> <ref>Lu Nicoll 2009</ref>



	==FOOTNOTES==		==FOOTNOTES==

Bradley Monk at 05:22, 2 January 2015

2015-01-02T05:22:21Z

← Older revision		Revision as of 22:22, 1 January 2015
Line 287:		Line 287:
	* 156. Hoze, N. et al. Heterogeneity of AMPA receptor trafficking and molecular interactions revealed by superresolution analysis of live cell imaging. Proc Natl Acad Sci U S A 109, 17052-7 (2012).		* 156. Hoze, N. et al. Heterogeneity of AMPA receptor trafficking and molecular interactions revealed by superresolution analysis of live cell imaging. Proc Natl Acad Sci U S A 109, 17052-7 (2012).
	* 157. Renner, M., Choquet, D. & Triller, A. Control of the postsynaptic membrane viscosity. J Neurosci 29, 2926-37 (2009).		* 157. Renner, M., Choquet, D. & Triller, A. Control of the postsynaptic membrane viscosity. J Neurosci 29, 2926-37 (2009).

			==Wiki References]]
			<references/>

Bradley Monk: /* DO CTAILS OR TARPS REGULATE AMPAR TRAFFICKING? */

2015-01-02T05:21:06Z

DO CTAILS OR TARPS REGULATE AMPAR TRAFFICKING?

@@ Line 103: / Line 103: @@
 ==DO CTAILS OR TARPS REGULATE AMPAR TRAFFICKING?==
-From the large body of work one gets the sense that nearly every operative step in the lifetime of an AMPAR depends on Ctails interactions with PDZ and other regulatory proteins, and yet all these same steps seem to involve TARP interactions 113. Moreover, how are subunit-specific trafficking effects observed when TARPs lack subunit specificity? The most straightforward answer would be if TARPs complex with AMPARs early on in biogenesis, where aid in tetramer formation, ER export, cytosolic transport, and surface expression. After the TARP-AMPAR complex reaches the surface they dissociated and part ways.
+From the large body of work one gets the sense that nearly every operative step in the lifetime of an AMPAR depends on Ctails interactions with PDZ and other regulatory proteins, and yet all these same steps seem to involve TARP interactions 114. Moreover, how are subunit-specific trafficking effects observed when TARPs lack subunit specificity 115? The most straightforward answer would be if TARPs complex with AMPARs early on in biogenesis, where aid in tetramer formation, ER export, cytosolic transport, and surface expression. After the TARP-AMPAR complex reaches the surface they dissociated and part ways. Alternatively, the reverse scenario may be true, where MAGUK proteins help along the secretory pathway, transitioning AMPARs from the ER and Golgi systems out to dendritic arbors. As mentioned above, SAP97 is known to associate with GluR1 to a much greater extent in these organelles than at synapses 86. However, this may change later in development, after various other subunit-specific binding proteins like GRIP and ABP mobilize into synapses to accommodate subunit-specific trafficking (reviewed in 94).
@@ Line 112: / Line 129: @@
 <br>
 ==REFERENCES==
 * 1.         Bristol, U.o. in Neural pathways (2014).

Bradley Monk: /* REFERENCES */

2014-12-31T08:24:16Z

REFERENCES

← Older revision		Revision as of 01:24, 31 December 2014
Line 271:		Line 271:
	* 156. Hoze, N. et al. Heterogeneity of AMPA receptor trafficking and molecular interactions revealed by superresolution analysis of live cell imaging. Proc Natl Acad Sci U S A 109, 17052-7 (2012).		* 156. Hoze, N. et al. Heterogeneity of AMPA receptor trafficking and molecular interactions revealed by superresolution analysis of live cell imaging. Proc Natl Acad Sci U S A 109, 17052-7 (2012).
	* 157. Renner, M., Choquet, D. & Triller, A. Control of the postsynaptic membrane viscosity. J Neurosci 29, 2926-37 (2009).		* 157. Renner, M., Choquet, D. & Triller, A. Control of the postsynaptic membrane viscosity. J Neurosci 29, 2926-37 (2009).
	*
	*
			==FOOTNOTES==
	* [i] Expression of a protein on a null background involves using CRE to selectively excise genes that have been previously flanked by LoxP sites. In this case genes coding for GluA1-3 were removed by CRE, resulting in the complete absence of AMPARs. On this AMPAR-null background, mutant GluR can then be expressed to isolate effects limited to a single subunit. The term overexpression refers to a method where virus or biolistic transfection is used to insert an extra copy of some gene on a wild-type background (one where the endogenous gene is left intact); since there are now two (or more) copies of that gene encoding for a single type of protein, overexpressed genes often result in overexpressed proteins compared to the wild-type.		* [i] Expression of a protein on a null background involves using CRE to selectively excise genes that have been previously flanked by LoxP sites. In this case genes coding for GluA1-3 were removed by CRE, resulting in the complete absence of AMPARs. On this AMPAR-null background, mutant GluR can then be expressed to isolate effects limited to a single subunit. The term overexpression refers to a method where virus or biolistic transfection is used to insert an extra copy of some gene on a wild-type background (one where the endogenous gene is left intact); since there are now two (or more) copies of that gene encoding for a single type of protein, overexpressed genes often result in overexpressed proteins compared to the wild-type.
	* [ii] Interestingly, despite it’s significantly reduced surface expression, GluR1ΔC rescued EPSCs to the same degree as full-length GluR1.		* [ii] Interestingly, despite it’s significantly reduced surface expression, GluR1ΔC rescued EPSCs to the same degree as full-length GluR1.