A CaVβ SH3/Guanylate Kinase Domain Interaction Regulates Multiple Properties of Voltage-gated Ca2+ Channels

Auxiliary Ca2+ channel β subunits (CaVβ) regulate cellular Ca2+ signaling by trafficking pore-forming α1 subunits to the membrane and normalizing channel gating. These effects are mediated through a characteristic src homology 3/guanylate kinase (SH3–GK) structural module, a design feature shared in common with the membrane-associated guanylate kinase (MAGUK) family of scaffold proteins. However, the mechanisms by which the CaVβ SH3–GK module regulates multiple Ca2+ channel functions are not well understood. Here, using a split-domain approach, we investigated the role of the interrelationship between CaVβ SH3 and GK domains in defining channel properties. The studies build upon a previously identified split-domain pair that displays a trans SH3–GK interaction, and fully reconstitutes CaVβ effects on channel trafficking, activation gating, and increased open probability (Po). Here, by varying the precise locations used to separate SH3 and GK domains and monitoring subsequent SH3–GK interactions by fluorescence resonance energy transfer (FRET), we identified a particular split-domain pair that displayed a subtly altered configuration of the trans SH3–GK interaction. Remarkably, this pair discriminated between CaVβ trafficking and gating properties: α1C targeting to the membrane was fully reconstituted, whereas shifts in activation gating and increased Po functions were selectively lost. A more extreme case, in which the trans SH3–GK interaction was selectively ablated, yielded a split-domain pair that could reconstitute neither the trafficking nor gating-modulation functions, even though both moieties could independently engage their respective binding sites on the α1C (CaV1.2) subunit. The results reveal that CaVβ SH3 and GK domains function codependently to tune Ca2+ channel trafficking and gating properties, and suggest new paradigms for physiological and therapeutic regulation of Ca2+ channel activity

Topoisomerase 1 inhibition reversibly impairs synaptic function

Topoisomerases are enzymes that resolve DNA supercoiling during cell division and gene transcription. Inhibitors of these enzymes are used to treat multiple forms of cancer. Recently we found that topoisomerase inhibitors have profound effects on synaptic genes expressed in the brain. Here we examine the contribution of a clinically used topoisomerase inhibitor on the expression of synaptic proteins and synaptic transmission. We find that inhibition of topoisomerase 1 (TOP1) dampens excitatory and inhibitory synaptic transmission in cortical neurons. Additionally, these effects are fully reversible, because synaptic protein levels and synaptic transmission recover upon washout of the TOP1 inhibitor. These findings provide insights into how inhibition of TOP1 impacts synaptic function in neurons

Synapse-Specific Control of Experience-Dependent Plasticity by Presynaptic NMDA Receptors

Sensory experience orchestrates the development of cortical circuitry by adaptively modifying neuro-transmission and synaptic connectivity. However, the mechanisms underlying these experience-dependent modifications remain elusive. Here we demonstrate that visual experience suppresses a presynaptic NMDA receptor (preNMDAR)-mediated form of timing-dependent long-term depression (tLTD) at visual cortex layer (L) 4-2/3 synapses. This tLTD can be maintained during development, or reinstated in adulthood, by sensory deprivation. The changes in tLTD are mirrored by changes in glutamate release; visual deprivation enhances both tLTD and glutamate release. These effects require the GluN3A NMDAR subunit, the levels of which are increased by visual deprivation. Further, by coupling the pathway-specific optogenetic induction of tLTD with cell-type-specific NMDAR deletion, we find that visual experience modifies preNMDAR-mediated plasticity specifically at L4-L2/3 synapses

Synapse-Specific Control of Experience-Dependent Plasticity by Presynaptic NMDA Receptors

Sensory experience orchestrates the development of cortical circuitry by adaptively modifying neuro-transmission and synaptic connectivity. However, the mechanisms underlying these experience-dependent modifications remain elusive. Here we demonstrate that visual experience suppresses a presynaptic NMDA receptor (preNMDAR)-mediated form of timing-dependent long-term depression (tLTD) at visual cortex layer (L) 4-2/3 synapses. This tLTD can be maintained during development, or reinstated in adulthood, by sensory deprivation. The changes in tLTD are mirrored by changes in glutamate release; visual deprivation enhances both tLTD and glutamate release. These effects require the GluN3A NMDAR subunit, the levels of which are increased by visual deprivation. Further, by coupling the pathway-specific optogenetic induction of tLTD with cell-type-specific NMDAR deletion, we find that visual experience modifies preNMDAR-mediated plasticity specifically at L4-L2/3 synapses

Synapse-specific control of experience-dependent plasticity by presynaptic NMDA receptors.

Sensory experience orchestrates the development of cortical circuitry by adaptively modifying neurotransmission and synaptic connectivity. However, the mechanisms underlying these experience-dependent modifications remain elusive. Here we demonstrate that visual experience suppresses a presynaptic NMDA receptor (preNMDAR)-mediated form of timing-dependent long-term depression (tLTD) at visual cortex layer (L) 4-2/3 synapses. This tLTD can be maintained during development, or reinstated in adulthood, by sensory deprivation. The changes in tLTD are mirrored by changes in glutamate release; visual deprivation enhances both tLTD and glutamate release. These effects require the GluN3A NMDAR subunit, the levels of which are increased by visual deprivation. Further, by coupling the pathway-specific optogenetic induction of tLTD with cell-type-specific NMDAR deletion, we find that visual experience modifies preNMDAR-mediated plasticity specifically at L4-L2/3 synapses

Synapse-specific control of experience-dependent plasticity by presynaptic NMDA receptors.

Sensory experience orchestrates the development of cortical circuitry by adaptively modifying neurotransmission and synaptic connectivity. However, the mechanisms underlying these experience-dependent modifications remain elusive. Here we demonstrate that visual experience suppresses a presynaptic NMDA receptor (preNMDAR)-mediated form of timing-dependent long-term depression (tLTD) at visual cortex layer (L) 4-2/3 synapses. This tLTD can be maintained during development, or reinstated in adulthood, by sensory deprivation. The changes in tLTD are mirrored by changes in glutamate release; visual deprivation enhances both tLTD and glutamate release. These effects require the GluN3A NMDAR subunit, the levels of which are increased by visual deprivation. Further, by coupling the pathway-specific optogenetic induction of tLTD with cell-type-specific NMDAR deletion, we find that visual experience modifies preNMDAR-mediated plasticity specifically at L4-L2/3 synapses