Diffusion and Not Active Transport Underlies and Limits ERK1/2 Synapse-to-Nucleus Signaling in Hippocampal Neurons

Abstract

The propagation of signals from synapses and dendrites to the nucleus is crucial for long lasting adaptive changes in the nervous system. The ERK-MAPK pathway can link neuronal activity and cell surface receptor activation to the regulation of gene transcription, and it is often considered the principal mediator of synapse-to-nucleus communication in late-phase plasticity and learning. However, the mechanisms underlying ERK1/2 trafficking in dendrites and nuclear translocation in neurons remain to be determined leaving it unclear whether ERK1/2 activated at the synapse can contribute to nuclear signaling and transcriptional regulation. Using the photobleachable and photoactivable fluorescent tag Dronpa on ERK1 and ERK2, we show here that ERK1/2 translocation to the nucleus of hippocampal neurons is induced by the stimulation of N-methyl-D-aspartate receptors or TrkB stimulation and is apparently mediated by facilitated diffusion. In contrast, ERK1/2 trafficking within dendrites is not signal-regulated and is mediated by passive diffusion. Within dendrites, the reach of a locally activated pool of ERK1/2 is very limited and follows an exponential decay with distance. These results indicate that successful signal propagation to the nucleus by the ERK-MAPK pathway depends on the distance of the nucleus from the site of ERK1/2 activation. ERK1/2 activated within or near the soma may rapidly reach the nucleus to induce gene expression, whereas ERK1/2 activated at distal synapses may only contribute to local signaling.The extracellular signal-regulated kinase/mitogen-activated protein (ERK-MAP) 2 kinase cascade is a multifunctional signaling module that plays an important role in the development, differentiation, and proliferation of many cell types. In the nervous system, ERK1 and ERK2 are activated by trophic factors, such as BDNF (1) and electrical activity causing calcium influx into neurons through NMDA receptors or voltage-gated calcium channels (2, 3). A large body of literature has implicated the ERK-MAP kinase pathway in numerous activity-driven neuronal processes, including neuronal survival, synaptic plasticity and learning (4, 5), circadian rhythms (6), pain (7), and addiction (8). ERK1/2 can act locally near the site of activation by cell surface receptors or ion channels to control, for example, the trafficking of ␣-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (9). Another putative role of ERK1/2 in the nervous system is to propagate signals generated at the synapse along the dendrites toward and into the cell nucleus, where it leads to induction of gene transcription. ERK1/2 can phosphorylate several transcription factors, including the ternary complex factors Elk-1 (10, 11) and SAP-1/2 (12), as well as c-Jun (13) and c-Fos (14). The cAMP-response element-binding protein (CREB) is also a target of the ERK-MAP kinase pathway, although CREB phosphorylation on its activator site serine 133 is catalyzed not by ERK1/2 but by the ERK1/2-regulated kinases ribosomal protein S6 kinase 2 and mitog...

Stimulated nuclear translocation of NF-κB and shuttling differentially depend on dynein and the dynactin complex

“…Interestingly, dynein knockdown did not significantly alter either CREB or NFAT reporter activity, although it has been reported that perturbations in the microtubule network could inhibit NFAT (32). While p53 is known to use dynein (26), the transport mechanisms of many nuclear localizing molecules are either unknown or are independent of the cytoskeleton (29,33,34). The further understanding of both dynein-dependent and independent mechanisms of NF-B transport may reveal additional regulatory points in this widespread signaling pathway.…”

Nuclear Calcium Buffering Capacity Shapes Neuronal Architecture

“…DNA transfection was performed after a culturing period of 8 days in vitro (DIV) using Lipofectamine 2000 (Invitrogen) as described previously (20). Infection of neuronal cultures with rAAVs delivering the different expression constructs was performed on DIV 3-6.…”

Synaptic Activity Induces Dramatic Changes in the Geometry of the Cell Nucleus: Interplay between Nuclear Structure, Histone H3 Phosphorylation, and Nuclear Calcium Signaling

“…One of the intracellular signaling pathways activated by synaptic activity and a localized calcium signal in the immediate vicinity of synaptic NMDA receptors is the ERK-MAP kinase cascade (Bading and Greenberg, 1991;Grewal et al, 1999;Hardingham et al, 2001b;Sweatt, 2004;Wiegert et al, 2007). To investigate whether this signaling pathway is important for NMDA receptordependent regulation of nuclear geometry, we pharmacologically blocked this pathway using MAP kinase/ERK kinase (MEK) inhibitors PD98059 or UO126.…”