Dr. Colón-Ramos describes his group’s finding of a previously-unknown metabolic subcompartment that powers synaptic function. His group observed that under conditions of energy stress, glycolytic proteins, which are normally diffusely distributed in cells, co-localize to a punctate structure adjacent to synapses. The local formation of these complexes is required for the synaptic vesicle cycle and synaptic function. The discoveries contribute to an unsolved question in neuroscience: how local, rapid and transient changes in energy demands are met at synapses to sustain their function. He frames his lab’s cell biological findings in the context of the long history of research of energy metabolism, drawing new lessons and discussing how the discoveries now provide new opportunities to examine the cell biology of metabolism at the neuronal synapse.

Colón-Ramos discusses how his group uses the approaches they have developed to reduce system’s level questions, like behavior, to cell biological questions at the synapse. He describes his lab’s discovery that two plasticity mechanisms—sensory adaptation and presynaptic plasticity—act within a single cell in C. elegans to encode thermosensory information and actuate a temperature-preference memory. The integration of these plasticity mechanisms result in a single-cell logic system that can both represent sensory stimuli and guide memory-based behavioral preference. These findings allow the Colón-Ramos group to directly link cell biological changes at the neuronal synapse with memory and behavior.

Engert describes work done with collaborators to develop a robust operant learning assay for larval zebrafish.  Using this assay and techniques for measuring neuronal activity in tethered, awake fish, they are beginning to decipher what happens in a vertebrate brain while the animal is learning.

Neuronal activity can be triggered by either external stimuli or by stimuli that are a result of your own actions.  In his second talk, Engert explains how his lab measured and compared neuronal activity in response to these two types of stimuli. Using a set up where larval zebra fish are immobilized with drugs, yet the neurons which innervate the muscles fire normally, they measured neuronal activity in response to visual stimuli. By moving a virtual landscape quickly or slowly they could mimic fast or slow swimming by the fish.  Interestingly, they found that the fish would adjust its neuronal activity up or down so its perceived swim speed matched the movement of the virtual landscape or, in other words, so the external stimuli matched the expected result of its actions. Engert’s group mapped the neurons responsible for visual processing and locomotion, as well as those responsible for gain control up or down to match the fish’s swimming strength with the external stimuli.

Drubin describes how his lab began studying actin dynamics and endocytosis in yeast using two-color, real-time fluorescence and kymographs. These tools enabled his team to confirm that actin regulated clathrin-mediated endocytosis. They discovered that BAR and F-BAR proteins stabilized the process by acting as a scaffold for actin and facilitating invagination and fission of the cell membrane to develop vesicles.

Actin forms many cellular structures and regulates a variety of critical biological processes. Dr. David Drubin’s lab focuses on studying actin in the context of membrane trafficking. In his first iBiology seminar, Drubin recounts seminal research done using the intracellular pathogen Listeria that uncovered how the bacteria harnesses phagocytosis and actin polymerization to facilitate motility. These initial studies led to the discovery of key regulators of actin filament formation including Arp2/3 and N-WASP. Advances in yeast genetics, biochemistry and imaging then allowed Drubin and others to expand their studies to actin dynamics and endocytosis in yeast.

Drubin explains how he and his lab transferred their knowledge of endocytosis in yeast to determine how actin dynamics are harnessed to drive endocytic traffic in mammalian cells. In mammalian cells, his team observed the importance of actin-dynamin interactions in clathrin-dependent endocytosis. Interestingly, they found variability in endocytic site morphology and dynamics. Studies using stem cells suggested that this diversity in actin-mediated endocytosis is important for determining cell identity and development.

Drubin explains how endocytosis can be used as a system to dissect the mechanisms of actin dynamics in yeast.  He focuses on his lab’s research on three key processes: actin disassembly, filament capping and Arp2/3 nucleation.  By giving an overview of the importance of actin dynamics in regulating a single cell process, endocytosis, Drubin highlights the crucial role of actin assembly and disassembly in both yeast and mammalian cells.

A fundamental question in neuroscience is how synapses are assembled in living animals to produce behaviors and store memories. Dr. Daniel Colón-Ramos and his lab address these questions by studying the cell biology of the neuronal synapse. In the first part of his seminar series, he introduces approaches his group has pioneered and implemented to image and manipulate synapses in vivo and with single-cell resolution in the nematode C.elegans. He also discusses fundamental aspects of genetics, cell biology and neuroscience which are necessary for understanding his research program and, more generally, for understanding how scientists make use of model organisms to generate new knowledge.

Cheng shows how his laboratory has used Cryo-EM to study the atomic resolution of membrane proteins. It is challenging to use conventional methods to study membrane protein structure, given that the 3D structure of most membrane proteins is dependent on their interaction with the phospholipid bilayer. Cheng describes how his laboratory has overcome these challenges to successfully solve the protein structure of the TRPV1 ion channel in different conformations at atomic resolution. He describes the benefits of using of amphipols, lipid nanodiscs, and Fab-assisted approaches to facilitate structural studies.