PKA Activity-Driven Modulation of Bidirectional Long-Distance transport of Lysosomal vesicles During Synapse Maintenance.

The bidirectional long-distance transport of organelles is crucial for cell body-synapse communication. However, the mechanisms by which this transport is modulated for synapse formation, maintenance, and plasticity are not fully understood. Here, we demonstrate through quantitative analyses that maintaining sensory neuron-motor neuron synapses in the gill-siphon withdrawal reflex is linked to a sustained reduction in the retrograde transport of lysosomal vesicles in sensory neurons.

Single-neuron analysis of aging-associated changes in learning reveals impairments in transcriptional plasticity.

The molecular mechanisms underlying age-related declines in learning and long-term memory are still not fully understood. To address this gap, our study focused on investigating the transcriptional landscape of a singularly identified motor neuron L7 in Aplysia, which is pivotal in a specific type of nonassociative learning known as sensitization of the siphon-withdraw reflex. Employing total RNAseq analysis on a single isolated L7 motor neuron after short-term or long-term sensitization (LTS) training of Aplysia at 8, 10, and 12 months (representing mature, late mature, and senescent stages), we uncovered aberrant changes in transcriptional plasticity during the aging process.

Functional implication of the homotrimeric multidomain vacuolar sorting receptor 1 (VSR1) from Arabidopsis thaliana.

The vacuolar sorting receptors (VSRs) are specific to plants and are responsible for sorting and transporting particular proteins from the trans-Golgi network to the vacuole. This process is critically important for various cellular functions, including storing nutrients during seed development. Despite many years of intense studies on VSRs, a complete relation between function and structure has not yet been revealed.

Synaptically-targeted long non-coding RNA SLAMR promotes structural plasticity by increasing translation and CaMKII activity.

Long noncoding RNAs (lncRNAs) play crucial roles in maintaining cell homeostasis and function. However, it remains largely unknown whether and how neuronal activity impacts the transcriptional regulation of lncRNAs, or if this leads to synapse-related changes and contributes to the formation of long-term memories. Here, we report the identification of a lncRNA, SLAMR, which becomes enriched in CA1-hippocampal neurons upon contextual fear conditioning but not in CA3 neurons.

, a synaptically targeted lncRNA, facilitates the consolidation of contextual fear memory.

LncRNAs are involved in critical processes for cell homeostasis and function. However, it remains largely unknown whether and how the transcriptional regulation of long noncoding RNAs results in activity-dependent changes at the synapse and facilitate formation of long-term memories. Here, we report the identification of a novel lncRNA, SLAMR, that becomes enriched in CA1- but not in CA3-hippocampal neurons upon contextual fear conditioning.

Short-Term and Long-Term Sensitization Differentially Alters the Composition of an Anterograde Transport Complex in .

Long-term memory formation requires anterograde transport of proteins from the soma of a neuron to its distal synaptic terminals. This allows new synaptic connections to be grown and existing ones remodeled. However, we do not yet know which proteins are transported to synapses in response to activity and temporal regulation.

Axonal transport deficits in neuropsychiatric disorders.

Axonal transport is a major cellular process that mediates bidirectional signaling between the soma and synapse, enabling both intracellular and intercellular communications. Cellular materials, such as proteins, RNAs, and organelles, are transported by molecular motor proteins along cytoskeletal highways in a highly regulated manner. Several studies have demonstrated that axonal transport is central to normal neuronal function, plasticity, and memory storage.

Live Imaging and Quantitative Analysis of Organelle Transport in Sensory Neurons of Aplysia Californica.

Axonal transport moves proteins, RNAs, and organelles between the soma and synapses to support synaptic function and activity-dependent changes in synaptic strength. This transport is impaired in several neurodegenerative disorders such as Alzheimer's disease. Thus, it is critical to understand the regulation and underlying mechanisms of the transport process.

Molecular motor KIF3B in the prelimbic cortex constrains the consolidation of contextual fear memory.

Molecular and cellular mechanisms underlying the role of the prelimbic cortex in contextual fear memory remain elusive. Here we examined the kinesin family of molecular motor proteins (KIFs) in the prelimbic cortex for their role in mediating contextual fear, a form of associative memory. KIFs function as critical mediators of synaptic transmission and plasticity by their ability to modulate microtubule function and transport of gene products.

Molecular motor protein KIF5C mediates structural plasticity and long-term memory by constraining local translation.

Synaptic structural plasticity, key to long-term memory storage, requires translation of localized RNAs delivered by long-distance transport from the neuronal cell body. Mechanisms and regulation of this system remain elusive. Here, we explore the roles of KIF5C and KIF3A, two members of kinesin superfamily of molecular motors (Kifs), and find that loss of function of either kinesin decreases dendritic arborization and spine density whereas gain of function of KIF5C enhances it.

Activity-regulated synaptic targeting of lncRNA ADEPTR mediates structural plasticity by localizing Sptn1 and AnkB in dendrites.

Activity-dependent structural plasticity at the synapse requires specific changes in the neuronal transcriptome. While much is known about the role of coding elements in this process, the role of the long noncoding transcriptome remains elusive. Here, we report the discovery of an intronic long noncoding RNA (lncRNA)-termed ADEPTR-that is up-regulated and synaptically transported in a cAMP/PKA-dependent manner in hippocampal neurons, independently of its protein-coding host gene.

Double Duty: Mitotic Kinesins and Their Post-Mitotic Functions in Neurons.

Neurons, regarded as post-mitotic cells, are characterized by their extensive dendritic and axonal arborization. This unique architecture imposes challenges to how to supply materials required at distal neuronal components. Kinesins are molecular motor proteins that mediate the active delivery of cellular materials along the microtubule cytoskeleton for facilitating the local biochemical and structural changes at the synapse.

Molecular Motor KIF3B Acts as a Key Regulator of Dendritic Architecture in Cortical Neurons.

Neurons require a well-coordinated intercellular transport system to maintain their normal cellular function and morphology. The kinesin family of proteins (KIFs) fills this role by regulating the transport of a diverse array of cargos in post-mitotic cells. On the other hand, in mitotic cells, KIFs facilitate the fidelity of the cellular division machinery.

Neuron-based high-content assay and screen for CNS active mitotherapeutics.

Impaired mitochondrial dynamics and function are hallmarks of many neurological and psychiatric disorders, but direct screens for mitotherapeutics using neurons have not been reported. We developed a multiplexed and high-content screening assay using primary neurons and identified 67 small-molecule modulators of neuronal mitostasis (MnMs). Most MnMs that increased mitochondrial content, length, and/or health also increased mitochondrial function without altering neurite outgrowth.

Emerging roles for long noncoding RNAs in learning, memory and associated disorders.

While protein-coding genes have been widely studied in learning and memory, the role of the non-coding genome has only recently been investigated. With advances in high throughput sequencing technologies and functional profiling methods, multiple long noncoding RNAs (lncRNAs) have been functionally and mechanistically linked with neurobiological processes related with learning and memory, as well disorders that lead to memory impairment. However, these macromolecules are still a subject of controversy and intense scrutiny regarding the proper criteria for determining their functionality and their evolution in the central nervous system.

Synapse Formation Activates a Transcriptional Program for Persistent Enhancement in the Bi-directional Transport of Mitochondria.

Mechanisms that regulate the bi-directional transport of mitochondria in neurons for maintaining functional synaptic connections are poorly understood. Here, we show that in the pre-synaptic sensory neurons of the Aplysia gill withdrawal reflex, the formation of functional synapses leads to persistent enhancement in the flux of bi-directional mitochondrial transport. In the absence of a functional synapse, activation of cAMP signaling is sufficient to enhance bi-directional transport in sensory neurons.

Kinesin Family of Proteins Kif11 and Kif21B Act as Inhibitory Constraints of Excitatory Synaptic Transmission Through Distinct Mechanisms.

Despite our understanding of the functions of the kinesin family of motor proteins (Kifs) in neurons, their specific roles in neuronal communication are less understood. To address this, by carrying out RNAi-mediated loss of function studies, we assessed the necessity of 18 Kifs in excitatory synaptic transmission in mouse primary hippocampal neurons prepared from both sexes. Our measurements of excitatory post-synaptic currents (EPSCs) have identified 7 Kifs that were found to be not critical and 11 Kifs that are essential for synaptic transmission by impacting either frequency or amplitude or both components of EPSCs.

Long noncoding RNA GM12371 acts as a transcriptional regulator of synapse function.

Despite the growing evidence suggesting that long noncoding RNAs (lncRNAs) are critical regulators of several biological processes, their functions in the nervous system remain elusive. We have identified an lncRNA, GM12371, in hippocampal neurons that is enriched in the nucleus and necessary for synaptic communication, synapse density, synapse morphology, and dendritic tree complexity. Mechanistically, GM12371 regulates the expression of several genes involved in neuronal development and differentiation, as well as expression of specific lncRNAs and their cognate mRNA targets.

Encoding of contextual fear memory requires proteins in the prelimbic cortex.

Background: Despite our understanding of the significance of the prefrontal cortex in the consolidation of long-term memories (LTM), its role in the encoding of LTM remains elusive. Here we investigated the role of new protein synthesis in the mouse medial prefrontal cortex (mPFC) in encoding contextual fear memory.

Methods: Because a change in the association of mRNAs to polyribosomes is an indicator of new protein synthesis, we assessed the changes in polyribosome-associated mRNAs in the mPFC following contextual fear conditioning (CFC) in the mouse.

Automated measurement of fast mitochondrial transport in neurons.

There is growing recognition that fast mitochondrial transport in neurons is disrupted in multiple neurological diseases and psychiatric disorders. However, a major constraint in identifying novel therapeutics based on mitochondrial transport is that the large-scale analysis of fast transport is time consuming. Here we describe methodologies for the automated analysis of fast mitochondrial transport from data acquired using a robotic microscope.

Pharmacological Selectivity Within Class I Histone Deacetylases Predicts Effects on Synaptic Function and Memory Rescue.

Histone deacetylases (HDACs) are promising therapeutic targets for neurological and psychiatric disorders that impact cognitive ability, but the relationship between various HDAC isoforms and cognitive improvement is poorly understood, particularly in mouse models of memory impairment. A goal shared by many is to develop HDAC inhibitors with increased isoform selectivity in order to reduce unwanted side effects, while retaining procognitive effects. However, studies addressing this tack at the molecular, cellular and behavioral level are limited.

Transcriptome analyses of adult mouse brain reveal enrichment of lncRNAs in specific brain regions and neuronal populations.

Despite the importance of the long non-coding RNAs (lncRNAs) in regulating biological functions, the expression profiles of lncRNAs in the sub-regions of the mammalian brain and neuronal populations remain largely uncharacterized. By analyzing RNASeq datasets, we demonstrate region specific enrichment of populations of lncRNAs and mRNAs in the mouse hippocampus and pre-frontal cortex (PFC), the two major regions of the brain involved in memory storage and neuropsychiatric disorders. We identified 2759 lncRNAs and 17,859 mRNAs in the hippocampus and 2561 lncRNAs and 17,464 mRNAs expressed in the PFC.

Dissecting mechanisms of brain aging by studying the intrinsic excitability of neurons.

Several studies using vertebrate and invertebrate animal models have shown aging associated changes in brain function. Importantly, changes in soma size, loss or regression of dendrites and dendritic spines and alterations in the expression of neurotransmitter receptors in specific neurons were described. Despite this understanding, how aging impacts intrinsic properties of individual neurons or circuits that govern a defined behavior is yet to be determined.

High-throughput screening for small molecule modulators of motor protein Kinesin.

The kinesin superfamily of motor proteins are involved in the active transport of a large number of cargos such as organelles, proteins, and RNAs from the neuronal cell body to distal neuronal processes. Previously, we have shown that kinesin-mediated axonal transport of proteins and RNAs are important for long-term memory storage. Identification of small molecules that can activate or inhibit kinesins is of specific interest due to the significance of kinesin-mediated functions in neuronal health and plasticity.