@article {69756, title = {Periodic ER-plasma membrane junctions support long-range Ca signal integration in dendrites.}, journal = {Cell}, volume = {188}, year = {2025}, month = {01/2025}, pages = {484-500.e22}, abstract = {

Neuronal dendrites must relay synaptic inputs over long distances, but the mechanisms by which activity-evoked intracellular signals propagate over macroscopic distances remain unclear. Here, we discovered a system of periodically arranged endoplasmic reticulum-plasma membrane (ER-PM) junctions tiling the plasma membrane of dendrites at \~{}1\ μm intervals, interlinked by a meshwork of ER tubules patterned in a ladder-like array. Populated with Junctophilin-linked plasma membrane voltage-gated Ca channels and ER Ca-release channels (ryanodine receptors), ER-PM junctions are hubs for ER-PM crosstalk, fine-tuning of Ca homeostasis, and local activation of the Ca/calmodulin-dependent protein kinase II. Local spine stimulation activates the Ca modulatory machinery, facilitating signal transmission and ryanodine-receptor-dependent Ca release at ER-PM junctions over 20\ μm away. Thus, interconnected ER-PM junctions support signal propagation and Ca release from the spine-adjacent ER. The capacity of this subcellular architecture to modify both local and distant membrane-proximal biochemistry potentially contributes to dendritic computations.

}, keywords = {Animals, Calcium, Calcium Signaling, Calcium-Calmodulin-Dependent Protein Kinase Type 2, Cell Membrane, Dendrites, Endoplasmic Reticulum, Hippocampus, Humans, Male, Mice, Rats, Ryanodine Receptor Calcium Release Channel}, issn = {1097-4172}, doi = {10.1016/j.cell.2024.11.029}, author = {Benedetti, Lorena and Fan, Ruolin and Weigel, Aubrey V and Moore, Andrew S and Houlihan, Patrick R and Kittisopikul, Mark and Park, Grace and Petruncio, Alyson and Hubbard, Philip M and Pang, Song and Xu, C Shan and Hess, Harald F and Saalfeld, Stephan and Rangaraju, Vidhya and Clapham, David E and De Camilli, Pietro and Ryan, Timothy A and Lippincott-Schwartz, Jennifer} } @article {69420, title = {An interphase actin wave promotes mitochondrial content mixing and organelle homeostasis.}, journal = {Nat Commun}, volume = {15}, year = {2024}, month = {2024 May 07}, pages = {3793}, abstract = {

Across the cell cycle, mitochondrial dynamics are regulated by a cycling wave of actin polymerization/depolymerization. In metaphase, this wave induces actin comet tails on mitochondria that propel these organelles to drive spatial mixing, resulting in their equitable inheritance by daughter cells. In contrast, during interphase the cycling actin wave promotes localized mitochondrial fission. Here, we identify the F-actin nucleator/elongator FMNL1 as a positive regulator of the wave. FMNL1-depleted cells exhibit decreased mitochondrial polarization, decreased mitochondrial oxygen consumption, and increased production of reactive oxygen species. Accompanying these changes is a loss of hetero-fusion of wave-fragmented mitochondria. Thus, we propose that the interphase actin wave maintains mitochondrial homeostasis by promoting mitochondrial content mixing. Finally, we investigate the mechanistic basis for the observation that the wave drives mitochondrial motility in metaphase but mitochondrial fission in interphase. Our data indicate that when the force of actin polymerization is resisted by mitochondrial tethering to microtubules, as in interphase, fission results.

}, keywords = {Actins, Animals, Formins, Hela Cells, Homeostasis, Humans, Interphase, Microtubules, Mitochondria, Mitochondrial Dynamics, Mitochondrial Proteins, Reactive Oxygen Species}, issn = {2041-1723}, doi = {10.1038/s41467-024-48189-1}, author = {Coscia, Stephen M and Moore, Andrew S and Thompson, Cameron P and Tirrito, Christian F and Ostap, E Michael and Holzbaur, Erika L F} } @article {69400, title = {Mitochondrially-associated actin waves maintain organelle homeostasis and equitable inheritance.}, journal = {Curr Opin Cell Biol}, volume = {88}, year = {2024}, month = {2024 Apr 30}, pages = {102364}, abstract = {

First identified in dividing cells as revolving clusters of actin filaments, these are now understood as mitochondrially-associated actin waves that are active throughout the cell cycle. These waves are formed from the polymerization of actin onto a subset of mitochondria. Within minutes, this F-actin depolymerizes while newly formed actin filaments assemble onto neighboring mitochondria. In interphase, actin waves locally fragment the mitochondrial network, enhancing mitochondrial content mixing to maintain organelle homeostasis. In dividing cells actin waves spatially mix mitochondria in the mother cell to ensure equitable partitioning of these organelles between daughter cells. Progress has been made in understanding the consequences of actin cycling as well as the underlying molecular mechanisms, but many questions remain, and here we review these elements. Also, we draw parallels between mitochondrially-associated actin cycling and cortical actin waves. These dynamic systems highlight the remarkable plasticity of the actin cytoskeleton.

}, issn = {1879-0410}, doi = {10.1016/j.ceb.2024.102364}, author = {Coscia, Stephen M and Moore, Andrew S and Wong, Yvette C and Holzbaur, Erika L F} } @article {69169, title = {Motion of VAPB molecules reveals ER-mitochondria contact site subdomains.}, journal = {Nature}, volume = {626}, year = {2024}, month = {2024 Jan 24}, pages = {169-176}, abstract = {

To coordinate cellular physiology, eukaryotic cells rely on the rapid exchange of molecules at specialized organelle-organelle contact sites. Endoplasmic reticulum-mitochondrial contact sites (ERMCSs) are particularly vital communication hubs, playing key roles in the exchange of signalling molecules, lipids and metabolites. ERMCSs are maintained by interactions between complementary tethering molecules on the surface of each organelle. However, due to the extreme sensitivity of these membrane interfaces to experimental perturbation, a clear understanding of their nanoscale organization and regulation is still lacking. Here we combine three-dimensional electron microscopy with high-speed molecular tracking of a model organelle tether, Vesicle-associated membrane protein (VAMP)-associated protein B (VAPB), to map the structure and diffusion landscape of ERMCSs. We uncovered dynamic subdomains within VAPB contact sites that correlate with ER membrane curvature and undergo rapid remodelling. We show that VAPB molecules enter and leave ERMCSs within seconds, despite the contact site itself remaining stable over much longer time scales. This metastability allows ERMCSs to remodel with changes in the physiological environment to accommodate metabolic needs of the cell. An amyotrophic lateral sclerosis-associated mutation in VAPB perturbs these subdomains, likely impairing their remodelling capacity and resulting in impaired interorganelle communication. These results establish high-speed single-molecule imaging as a new tool for mapping the structure of contact site interfaces and reveal that the diffusion landscape of VAPB at contact sites is a crucial component of ERMCS homeostasis.

}, keywords = {Amyotrophic Lateral Sclerosis, Endoplasmic Reticulum, Humans, Mitochondria, Mitochondrial Membranes, Signal Transduction, Vesicular Transport Proteins}, issn = {1476-4687}, doi = {10.1038/s41586-023-06956-y}, author = {Obara, Christopher J and Nixon-Abell, Jonathon and Moore, Andrew S and Riccio, Federica and Hoffman, David P and Shtengel, Gleb and Xu, C Shan and Schaefer, Kathy and Pasolli, H Amalia and Masson, Jean-Baptiste and Hess, Harald F and Calderon, Christopher P and Blackstone, Craig and Lippincott-Schwartz, Jennifer} } @article {69704, title = {Periodic ER-plasma membrane junctions support long-range Ca signal integration in dendrites.}, journal = {Cell}, year = {2024}, month = {2024 Dec 18}, abstract = {

Neuronal dendrites must relay synaptic inputs over long distances, but the mechanisms by which activity-evoked intracellular signals propagate over macroscopic distances remain unclear. Here, we discovered a system of periodically arranged endoplasmic reticulum-plasma membrane (ER-PM) junctions tiling the plasma membrane of dendrites at \~{}1\ μm intervals, interlinked by a meshwork of ER tubules patterned in a ladder-like array. Populated with Junctophilin-linked plasma membrane voltage-gated Ca channels and ER Ca-release channels (ryanodine receptors), ER-PM junctions are hubs for ER-PM crosstalk, fine-tuning of Ca homeostasis, and local activation of the Ca/calmodulin-dependent protein kinase II. Local spine stimulation activates the Ca modulatory machinery, facilitating signal transmission and ryanodine-receptor-dependent Ca release at ER-PM junctions over 20\ μm away. Thus, interconnected ER-PM junctions support signal propagation and Ca release from the spine-adjacent ER. The capacity of this subcellular architecture to modify both local and distant membrane-proximal biochemistry potentially contributes to dendritic computations.

}, issn = {1097-4172}, doi = {10.1016/j.cell.2024.11.029}, author = {Benedetti, Lorena and Fan, Ruolin and Weigel, Aubrey V and Moore, Andrew S and Houlihan, Patrick R and Kittisopikul, Mark and Park, Grace and Petruncio, Alyson and Hubbard, Philip M and Pang, Song and Xu, C Shan and Hess, Harald F and Saalfeld, Stephan and Rangaraju, Vidhya and Clapham, David E and De Camilli, Pietro and Ryan, Timothy A and Lippincott-Schwartz, Jennifer} } @article {69472, title = {The physical and cellular mechanism of structural color change in zebrafish.}, journal = {Proc Natl Acad Sci U S A}, volume = {121}, year = {2024}, month = {2024 Jun 04}, pages = {e2308531121}, abstract = {

Many animals exhibit remarkable colors that are produced by the constructive interference of light reflected from arrays of intracellular guanine crystals. These animals can fine-tune their crystal-based structural colors to communicate with each other, regulate body temperature, and create camouflage. While it is known that these changes in color are caused by changes in the angle of the crystal arrays relative to incident light, the cellular machinery that drives color change is not understood. Here, using a combination of 3D focused ion beam scanning electron microscopy (FIB-SEM), micro-focused X-ray diffraction, superresolution fluorescence light microscopy, and pharmacological perturbations, we characterized the dynamics and 3D cellular reorganization of crystal arrays within zebrafish iridophores during norepinephrine (NE)-induced color change. We found that color change results from a coordinated 20{\textdegree} tilting of the intracellular crystals, which alters both crystal packing and the angle at which impinging light hits the crystals. Importantly, addition of the dynein inhibitor dynapyrazole-a completely blocked this NE-induced red shift by hindering crystal dynamics upon NE addition. FIB-SEM and microtubule organizing center (MTOC) mapping showed that microtubules arise from two MTOCs located near the poles of the iridophore and run parallel to, and in between, individual crystals. This suggests that dynein drives crystal angle change in response to NE by binding to the limiting membrane surrounding individual crystals and walking toward microtubule minus ends. Finally, we found that intracellular cAMP regulates the color change process. Together, our results provide mechanistic insight into the cellular machinery that drives structural color change.

}, keywords = {Animals, Color, Microscopy, Electron, Scanning, Norepinephrine, Pigmentation, Zebrafish, Zebrafish Proteins}, issn = {1091-6490}, doi = {10.1073/pnas.2308531121}, author = {Gur, Dvir and Moore, Andrew S and Deis, Rachael and Song, Pang and Wu, Xufeng and Pinkas, Iddo and Deo, Claire and Iyer, Nirmala and Hess, Harald F and Hammer, John A and Lippincott-Schwartz, Jennifer} } @article {69687, title = {Structural dynamics of human ribosomes in situ reconstructed by exhaustive high-resolution template matching.}, journal = {Mol Cell}, year = {2024}, month = {2024 Nov 25}, abstract = {

Protein synthesis is central to life and requires the ribosome, which catalyzes the stepwise addition of amino acids to a polypeptide chain by undergoing a sequence of structural transformations. Here, we employed high-resolution template matching (HRTM) on cryoelectron microscopy (cryo-EM) images of directly cryofixed living cells to obtain a set of ribosomal configurations covering the entire elongation cycle, with each configuration occurring at its native abundance. HRTM{\textquoteright}s position and orientation precision and ability to detect small targets (\~{}300\ kDa) made it possible to order these configurations along the reaction coordinate and to reconstruct molecular features of any configuration along the elongation cycle. Visualizing the cycle{\textquoteright}s structural dynamics by combining a sequence of \>40 reconstructions into a 3D movie readily revealed component and ligand movements, some of them surprising, such as spring-like intramolecular motion, providing clues about the molecular mechanisms involved in some still mysterious steps during chain elongation.

}, issn = {1097-4164}, doi = {10.1016/j.molcel.2024.11.003}, author = {Rickgauer, J Peter and Choi, Heejun and Moore, Andrew S and Denk, Winfried and Lippincott-Schwartz, Jennifer} } @article {68798, title = {Structural Diversity within the Endoplasmic Reticulum-From the Microscale to the Nanoscale.}, journal = {Cold Spring Harbor Perspectives in Biology}, volume = {15}, year = {2023}, month = {2023 Jun 01}, abstract = {

The endoplasmic reticulum (ER) is a continuous, highly dynamic membrane compartment that is crucial for numerous basic cellular functions. The ER stretches from the nuclear envelope to the outer periphery of all living eukaryotic cells. This ubiquitous organelle shows remarkable structural complexity, adopting a range of shapes, curvatures, and length scales. Canonically, the ER is thought to be composed of two simple membrane elements: sheets and tubules. However, recent advances in superresolution light microscopy and three-dimensional electron microscopy have revealed an astounding diversity of nanoscale ER structures, greatly expanding our view of ER organization. In this review, we describe these diverse ER structures, focusing on what is known of their regulation and associated functions in mammalian cells.

}, keywords = {Animals, Endoplasmic Reticulum, Mammals, Microscopy, Electron, Nuclear Envelope}, issn = {1943-0264}, doi = {10.1101/cshperspect.a041259}, author = {Obara, Christopher J and Moore, Andrew S and Lippincott-Schwartz, Jennifer} } @article {68369, title = {Structural Diversity within the Endoplasmic Reticulum-From the Microscale to the Nanoscale.}, journal = {Cold Spring Harbor Perspectives in Biology}, year = {2022}, month = {2022 Sep 19}, abstract = {

The endoplasmic reticulum (ER) is a continuous, highly dynamic membrane compartment that is crucial for numerous basic cellular functions. The ER stretches from the nuclear envelope to the outer periphery of all living eukaryotic cells. This ubiquitous organelle shows remarkable structural complexity, adopting a range of shapes, curvatures, and length scales. Canonically, the ER is thought to be composed of two simple membrane elements: sheets and tubules. However, recent advances in superresolution light microscopy and three-dimensional electron microscopy have revealed an astounding diversity of nanoscale ER structures, greatly expanding our view of ER organization. In this review, we describe these diverse ER structures, focusing on what is known of their regulation and associated functions in mammalian cells.

}, issn = {1943-0264}, doi = {10.1101/cshperspect.a041259}, author = {Obara, Christopher J and Moore, Andrew S and Lippincott-Schwartz, Jennifer} } @article {67177, title = {Actin cables and comet tails organize mitochondrial networks in mitosis.}, journal = {Nature}, volume = {591}, year = {2021}, month = {2021 Mar 03}, pages = {659-664}, abstract = {

Symmetric cell division requires the even partitioning of genetic information and cytoplasmic contents between daughter cells. Whereas the mechanisms coordinating the segregation of the genome are well known, the processes that ensure organelle segregation between daughter cells remain less well understood. Here we identify multiple actin assemblies with distinct but complementary roles in mitochondrial organization and inheritance in mitosis. First, we find a dense meshwork of subcortical actin cables assembled throughout the mitotic cytoplasm. This network scaffolds the endoplasmic reticulum and organizes three-dimensional mitochondrial positioning to ensure the equal segregation of mitochondrial mass at cytokinesis. Second, we identify a dynamic wave of actin filaments reversibly assembling on the surface of mitochondria during mitosis. Mitochondria sampled by this wave are enveloped within actin clouds that can spontaneously break symmetry to form elongated comet tails. Mitochondrial comet tails promote randomly directed bursts of movement that shuffle mitochondrial position within the mother cell to randomize inheritance of healthy and damaged mitochondria between daughter cells. Thus, parallel mechanisms mediated by the actin cytoskeleton ensure both equal and random inheritance of mitochondria in symmetrically dividing cells.

}, issn = {1476-4687}, doi = {10.1038/s41586-021-03309-5}, author = {Moore, Andrew S and Coscia, Stephen M and Simpson, Cory L and Ortega, Fabian E and Wait, Eric C and Heddleston, John M and Nirschl, Jeffrey J and Obara, Christopher J and Guedes-Dias, Pedro and Boecker, C Alexander and Chew, Teng-Leong and Theriot, Julie A and Lippincott-Schwartz, Jennifer and Holzbaur, Erika L F} } @article {67298, title = {Adhesion-mediated mechanosignaling forces mitohormesis.}, journal = {Cell Metabolism}, volume = {33}, year = {2021}, month = {2021 July 6}, pages = {1322}, abstract = {

Mitochondria control eukaryotic cell fate by producing the energy needed to support life and the signals required to execute programed cell death. The biochemical milieu is known to affect mitochondrial function and contribute to the dysfunctional mitochondrial phenotypes implicated in cancer and the morbidities of aging. However, the physical characteristics of the extracellular matrix are also altered in cancerous and aging tissues. Here, we demonstrate that cells sense the physical properties of the extracellular matrix and activate a mitochondrial stress response that adaptively tunes mitochondrial function via solute carrier family 9 member A1-dependent ion exchange and heat shock factor 1-dependent transcription. Overall, our data indicate that adhesion-mediated mechanosignaling may play an unappreciated role in the altered mitochondrial functions observed in aging and cancer.

}, issn = {1932-7420}, doi = {10.1016/j.cmet.2021.04.017}, author = {Tharp, Kevin M and Higuchi-Sanabria, Ryo and Timblin, Greg A and Ford, Breanna and Garzon-Coral, Carlos and Schneider, Catherine and Muncie, Jonathon M and Stashko, Connor and Daniele, Joseph R and Moore, Andrew S and Frankino, Phillip A and Homentcovschi, Stefan and Manoli, Sagar S and Shao, Hao and Richards, Alicia L and Chen, Kuei-Ho and Hoeve, Johanna Ten and Ku, Gregory M and Hellerstein, Marc and Nomura, Daniel K and Saijo, Karou and Gestwicki, Jason and Dunn, Alexander R and Krogan, Nevan J and Swaney, Danielle L and Dillin, Andrew and Weaver, Valerie M} } @article {65678, title = {Actin chromobody imaging reveals sub-organellar actin dynamics.}, journal = {Nature Methods}, volume = {17}, year = {2020}, month = {2020 Sep 01}, pages = {917-21}, abstract = {

The actin cytoskeleton plays multiple critical roles in cells, from cell migration to organelle dynamics. The small and transient actin structures regulating organelle dynamics are challenging to detect with fluorescence microscopy, making it difficult to determine whether actin filaments are directly associated with specific membranes. To address these limitations, we developed fluorescent-protein-tagged actin nanobodies, termed {\textquoteright}actin chromobodies{\textquoteright} (ACs), targeted to organelle membranes to enable high-resolution imaging of sub-organellar actin dynamics.

}, issn = {1548-7105}, doi = {10.1038/s41592-020-0926-5}, author = {Schiavon, Cara R and Zhang, Tong and Zhao, Bing and Moore, Andrew S and Wales, Pauline and Andrade, Leonardo R and Wu, Melissa and Sung, Tsung-Chang and Dayn, Yelena and Feng, Jasmine W and Quintero, Omar A and Shadel, Gerald S and Grosse, Robert and Manor, Uri} }