Ca^(2+)-regulated gene transcription is essential to diverse physiological processes, including the adaptive plasticity associated with learning. We found that basal synaptic input activates the NF-kB transcription factor by a pathway requiring the Ca^(2+)/calmodulin-dependent kinase CaMKII and local submembranous Ca^(2+) elevation. The p65:p50 NF-kB form is selectively localized at synapses; p65-deficient mice have no detectable synaptic NF-kB. Activated NF-kB moves to the nucleus and could directly transmute synaptic signals into altered gene expression. Mice lacking p65 show a selective learning deficit in the spatial version of the radial arm maze. These observations suggest that long-term changes to adult neuronal function caused by synaptic stimulation can be regulated by NF-kB nuclear translocation and gene activation

Baltimore, David

Chang, Jolene M.

Fanselow, Michael S.

Meffert, Mollie K.

Wiltgen, Brian J.

Caltech Authors - Main

Supplementary Methods
Constructs and Transfection
The GFPp65 construct was also put into a PUC backbone under control of the neuronal-
specific Thy-1 promoter (Thy-1 promoter was a kind gift from the laboratories of J.Sanes and
P.Caroni)S1. We chose the p65 NF-κB subunit for this construct because only p65 is capable
of upregulating its own inhibitor, IκBα. This might alleviate potential problems that could be
created if the fusion construct were over-expressed. A direct GFP-p65 fusion was chosen
because the sequence in linkers have sometimes been found to result in aberrant subcellular
localization. Tests of the GFPp65 construct in NIH 3T3 cells revealed that the GFP tag did
not interfere with normal cytoplasmic localization or nuclear translocation following TNF-α
stimulation.
Electrophoretic Mobility Shift Assay
EMSA and extract preparations were optimized using previous findingsS2. Several protease
inhibitors were included in extract buffers: leupeptin, aprotinin, pepstatin (all 5 µg / ml),
para-aminobenzamidine (0.5 mM) and PMSF (1mM). Supershift analysis was performed by
incubating monoclonal antibodies (Santa Cruz) for specific Rel family members in a pre-
binding reaction and then looking for band shifts on EMSA. Protein levels were made
equivalent in all binding reactions. DNA probes containing the following wild-type and
mutant κB consensus sequence were labeled with α-32P using a Klenow fill-in reaction:
Wild Type GGG GAC TTT CC
                  CCC  CTG AAA GG
  Mutant     GTT GAC TTT CC
                  CAA CTG AAA GG
Permeability and efficacy of the CaMKII inhibitor, antCNt, have been verified by
phosphorylation assays measuring inhibition of CaMKII activity after extracellular
application to HEK293 cells (effective inhibition was observed in the low µM range, J.Tsui
and K.U.Bayer, personal communication) and antCNt also provided inhibition in cellular
assays measuring CaMKII effect on dendritic mobility19. For experiments testing the effects
of constitutive CaMKII, T286D α-CaMKII (kindly provided by K.U. Bayer, Schulman
laboratory) was transfected into day 2 hippocampal cultures (Lipofectamine 2000,
Invitrogen), and crude nuclear extracts harvested for EMSA 72 hrs post-transfection.
Ribonuclease Protection Assay
Total RNA was prepared from neuronal cultures at selected time points following stimulation
by immediate homogenization in Tri Reagent (Molecular Research Center) and subsequent
RNA isolation. RPA probes were purchased (Pharmingen) and RPA performed according to
manufacturers instructions (Riboquant, Pharmingen). No binding was seen to yeast tRNA
used as a control for specificity. IκBα test probe was combined with probes for L32 and
GAPDH housekeeping genes. In the data analysis, this allowed the expression levels of each
sample (in each lane) to be normalized to the average of the two housekeeping genes. Percent
induction over non-stimulated controls was then calculated using normalized values.
Microscopy
FRAP was used to examine the dynamics of NF-κB in GFPp65 transfected neurons (36).
Neurons expressing relatively high levels of GFPp65 were found to contain both cytoplasmic
and nuclear GFP fluorescence, presumably because high expression overwhelmed the
endogenous capacity of binding proteins and/or IκB production. This could be largely
avoided by either co-coating the microcarrier beads with both GFPp65 and IκBα constructs,
or by titrating down the amount of GFPp65 DNA that was coated onto beads. We chose the
latter method to avoid introducing possible artifacts. Expression in the appropriate range was
judged by fluorescence intensity and the absence of visible nuclear fluorescence in
unstimulated cells. In neurons with high GFPp65 expression, FRAP experiments could not be
performed because GFP fluorescence diffused into the photobleached region even without
stimulation.
Reporter Assay
Virus was produced in 293 cells co-transfected with helper plasmids and supernatant
harvested and concentrated 48 hrs post-transfection45. Neurons were co-infected using master
mixes of reporter and LacZ virus for 24 hrs, incubated for 48 hrs or more, and stimulated in
triplicate. Viral infection had no apparent toxicity for neuronal cultures and expression could
be maintained for >3 weeks (the longest time examined) in healthy cultures as assessed using
a GFP-containing version of the lentivirus.
Behavioral Testing
 Although gross examination and immunostaining failed to distinguish brain tissue of
TNFR–/–p65–/– and TNFR–/–p65+/+ mice, it remains possible that subtle differences in neuronal
architexture and/or connectivity exist. When maintained in a reduced pathogen environment
these mice appeared to develop normally, survived for normal lifespans (>1 year), and did
not exhibit abnormal behavior. Matings of both heterozygous and homozygous mice were
successful in producing litters with genotypes at approximately expected Mendelian ratios.
Mice to be tested on the radial arm maze were transferred from Caltech to UCLA,
allowed one week to habituate to the new surroundings, and then begun on a week-long
gradual food deprivation period to achieve the target 85 % of free-feeding weight. During
food deprivation, mice received familiarization by feeding in the maze room and, on the
last three days of this period, were each handled by the experimenter for 2 min. Mice
were weighed daily and free-feeding time adjusted to maintain target weight.
Experimenters were blind to the genotypes of mice tested. Equal numbers of p65
wildtype and deficient mice were randomly selected and evaluated for infection by
nasopharyngeal and cecal cultures (diagnostics performed by RADIL) at the conclusion
of the experiments. There were no positive cultures.
The spatial version of the maze task consisted of two trials per day. The first trial
of each day was a sample trial in which the doors to four of the eight maze arms were
open and these arms were baited with food pellets. The second trial of the day was the
test trial where the doors to all arms were open and the four arms blocked in the sample
trial were now baited with food pellets. On both trials, the mouse was placed in the center
platform and allowed to explore freely until either all reward pellets were eaten or 5 min
elapsed. During the 5 min intertrial interval, mice were placed in a holding room while
the maze was cleansed to remove olfactory cues. Mice were tested for 20 days and
performance was scored for both within-trial errors (re-entry into an arm previously
entered on the same test trial) and between-trial errors (entry on the test trial to an arm
previously baited on that day's sample trial). Mice were also scored for the percent of
correct (baited) arms entered in the first four arm choices of the test trial; there are a total
of four baited arms in this trial. Both the order of individual mouse testing and the maze
arms blocked on the sample varied and were chosen randomly prior to the task.
The cued version of the maze task consisted of two identical trials per day. In
each trial the doors to all arms were open and four randomly selected arms were lit and
baited with food pellets. On both trials, the mouse was placed in the center platform and
allowed to explore freely until either all reward pellets were eaten or 5 min. elapsed. Each
time a mouse correctly entered a lit arm and consumed the food reward, the arm light was
promptly extinguished. During the 5 min intertrial interval, mice were placed in a holding
room while the maze was cleansed to remove olfactory cues. Mice were tested for 24
days and performance was scored for the percent of correct (lit and baited) arms entered
in the first four arm choices of the second trial of each day; there are a total of four lit and
baited arms in this trial. Following this testing period, a probe trial was conducted in
which each mouse was given 8 consecutive 2 min trials in which only one arm was lit
and baited; the last four of these trials were scored for percent correct (Fig 4d). Both the
order of individual mouse testing and the maze arms lit and baited varied and were
chosen randomly prior to the task.
In the spatial version of the RAM, attention to extramaze cues is required to avoid
both within trial and between trial errors. While p65-deficient mice achieved a within
trial error performance equivalent to p65-wildtype mice by day 9-10, they could not
consistently achieve equivalent performance of between trial errors until day 17 – 18
(Fig. 4a,b). This discrepancy is much greater than that seen for p65-wildtype mice (where
the two tasks are mastered within 2 days of eachother) and suggests that a learning deficit
is more likely to account for the difference than a deficit in attending to extramaze cues.
Nuclear translocation of NF-κB
Our FRAP experiments do not specifically exclude either diffusion or directed movement as
the mechanism of p65 translocation, although the finding of polarized movement does
suggest directed transport. Rates of p65 movement calculated from FRAP experiments (e.g.
between 5 - 10 min Fig.2c) are not wholly consistent with diffusional (proportional to t1/2) or
constant velocity (proportional to t) movement. Several explanations might account for this
finding. FRAP could depend upon multiple variable time constants, such as the pathway
leading to the asynchrononous phosphorylation and degradation of IκB. Alternatively, the
movement of individual molecules might occur not constantly, but intermittently, such as if
NF-κB were to bind on and off a transport protein, for example. It is also of interest that
molecules of p65 which reach the nucleus from distal processes following stimulation must
escape re-binding of IκB en-route. It is possible that the IκB-binding site of NF-κB is
concealed during translocation, perhaps by binding of the NLS to molecular transporters.
Mutation of the NLS of p65 does appear to interfere with nuclear translocation in neuronsS2.
Supplementary References
S1. Feng, G. et al. Imaging neuronal subsets in transgenic mice expressing multiple spectral
variants of GFP. Neuron 28, 41-51. (2000).
S2. Phelps, C. B., Sengchanthalangsy, L. L., Malek, S. & Ghosh, G. Mechanism of kappa B
DNA binding by Rel/NF-kappa B dimers. J Biol Chem 275, 24392-9. (2000).
S3. Korner, M., Rattner, A., Mauxion, F., Sen, R. & Citri, Y. A brain-specific transcription
activator. Neuron 3, 563-72. (1989).


NF-kB functions in synaptic signaling and behavior

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NF-kB functions in synaptic signaling and behavior

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