@article {68935, title = {Lysosomal release of amino acids at ER three-way junctions regulates transmembrane and secretory protein mRNA translation.}, journal = {bioRxiv}, year = {2023}, month = {2023 Aug 03}, abstract = {

One-third of the mammalian proteome is comprised of transmembrane and secretory proteins that are synthesized on endoplasmic reticulum (ER). Here, we investigate the spatial distribution and regulation of mRNAs encoding these membrane and secretory proteins (termed "secretome" mRNAs) through live cell, single molecule tracking to directly monitor the position and translation states of secretome mRNAs on ER and their relationship to other organelles. Notably, translation of secretome mRNAs occurred preferentially near lysosomes on ER marked by the ER junction-associated protein, Lunapark. Knockdown of Lunapark reduced the extent of secretome mRNA translation without affecting translation of other mRNAs. Less secretome mRNA translation also occurred when lysosome function was perturbed by raising lysosomal pH or inhibiting lysosomal proteases. Secretome mRNA translation near lysosomes was enhanced during amino acid deprivation. Addition of the integrated stress response inhibitor, ISRIB, reversed the translation inhibition seen in Lunapark knockdown cells, implying an eIF2 dependency. Altogether, these findings uncover a novel coordination between ER and lysosomes, in which local release of amino acids and other factors from ER-associated lysosomes patterns and regulates translation of mRNAs encoding secretory and membrane proteins.

}, doi = {10.1101/2023.08.01.551382}, author = {Choi, Heejun and Liao, Ya-Cheng and Yoon, Young J and Grimm, Jonathan and Lavis, Luke D and Singer, Robert H and Lippincott-Schwartz, Jennifer} } @article {67339, title = {Lipid droplets in the nervous system.}, journal = {Journal of Cell Biology}, volume = {220}, year = {2021}, month = {2021 Jul 05}, abstract = {

Lipid droplets are dynamic intracellular lipid storage organelles that respond to the physiological state of cells. In addition to controlling cell metabolism, they play a protective role for many cellular stressors, including oxidative stress. Despite prior descriptions of lipid droplets appearing in the brain as early as a century ago, only recently has the role of lipid droplets in cells found in the brain begun to be understood. Lipid droplet functions have now been described for cells of the nervous system in the context of development, aging, and an increasing number of neuropathologies. Here, we review the basic mechanisms of lipid droplet formation, turnover, and function and discuss how these mechanisms enable lipid droplets to function in different cell types of the nervous system under healthy and pathological conditions.

}, issn = {1540-8140}, doi = {10.1083/jcb.202102136}, author = {Ralhan, Isha and Chang, Chi-Lun and Lippincott-Schwartz, Jennifer and Ioannou, Maria S} } @article {64863, title = {A lipid-based partitioning mechanism for selective incorporation of proteins into membranes of HIV particles.}, journal = {Nature Cell Biology}, volume = {21}, year = {2019}, month = {2019 Apr}, pages = {452-461}, abstract = {

Particles that bud off from the cell surface, including viruses and microvesicles, typically have a unique membrane protein composition distinct from that of the originating plasma membrane. This selective protein composition enables viruses to evade the immune response and infect other cells. But how membrane proteins sort into budding viruses such as human immunodeficiency virus (HIV) remains unclear. Proteins could passively distribute into HIV-assembly-site membranes producing compositions resembling pre-existing plasma-membrane domains. Here, we demonstrate that proteins instead sort actively into HIV-assembly-site membranes, generating compositions enriched in cholesterol and sphingolipids that undergo continuous remodeling. Proteins are recruited into and removed from the HIV assembly site through lipid-based partitioning, initiated by oligomerization of the HIV structural protein Gag. Changes in membrane curvature at the assembly site further amplify this sorting process. Thus, a lipid-based sorting mechanism, aided by increasing membrane curvature, generates the unique membrane composition of the HIV surface.

}, issn = {1476-4679}, doi = {10.1038/s41556-019-0300-y}, author = {Sengupta, Prabuddha and Seo, Arnold Y and Pasolli, H Amalia and Song, Yul Eum and Johnson, Marc and Lippincott-Schwartz, Jennifer} } @article {48135, title = {Live cell single molecule-guided Bayesian localization super resolution microscopy.}, journal = {Cell Research}, year = {2016}, month = {2016 Dec 30}, issn = {1748-7838}, doi = {10.1038/cr.2015.160}, author = {Xu, Fan and Zhang, Mingshu and He, Wenting and Han, Renmin and Xue, Fudong and Liu, Zhiyong and Zhang, Fa and Lippincott-Schwartz, Jennifer and Xu, Pingyong} } @article {45617, title = {Lattice light-sheet microscopy: imaging molecules to embryos at high spatiotemporal resolution.}, journal = {Science}, volume = {346}, year = {2014}, month = {2014 Oct 24}, pages = {1257998}, abstract = {

Although fluorescence microscopy provides a crucial window into the physiology of living specimens, many biological processes are too fragile, are too small, or occur too rapidly to see clearly with existing tools. We crafted ultrathin light sheets from two-dimensional optical lattices that allowed us to image three-dimensional (3D) dynamics for hundreds of volumes, often at subsecond intervals, at the diffraction limit and beyond. We applied this to systems spanning four orders of magnitude in space and time, including the diffusion of single transcription factor molecules in stem cell spheroids, the dynamic instability of mitotic microtubules, the immunological synapse, neutrophil motility in a 3D matrix, and embryogenesis in Caenorhabditis elegans and Drosophila melanogaster. The results provide a visceral reminder of the beauty and the complexity of living systems.

}, issn = {1095-9203}, doi = {10.1126/science.1257998}, author = {Chen, Bi-Chang and Legant, Wesley R and Wang, Kai and Shao, Lin and Milkie, Daniel E and Davidson, Michael W and Janetopoulos, Chris and Wu, Xufeng S and Hammer, John A and Liu, Zhe and English, Brian P and Mimori-Kiyosue, Yuko and Romero, Daniel P and Ritter, Alex T and Lippincott-Schwartz, Jennifer and Fritz-Laylin, Lillian and Mullins, R Dyche and Mitchell, Diana M and Bembenek, Joshua N and Reymann, Anne-Cecile and B{\"o}hme, Ralph and Grill, Stephan W and Wang, Jennifer T and Seydoux, Geraldine and Tulu, U Serdar and Kiehart, Daniel P and Betzig, Eric} } @article {47630, title = {LKB1/AMPK and PKA control ABCB11 trafficking and polarization in hepatocytes.}, journal = {PloS one}, volume = {9}, year = {2014}, month = {2014}, pages = {e91921}, abstract = {

Polarization of hepatocytes is manifested by bile canalicular network formation and activation of LKB1 and AMPK, which control cellular energy metabolism. The bile acid, taurocholate, also regulates development of the canalicular network through activation of AMPK. In the present study, we used collagen sandwich hepatocyte cultures from control and liver-specific LKB1 knockout mice to examine the role of LKB1 in trafficking of ABCB11, the canalicular bile acid transporter. In polarized hepatocytes, ABCB11 traffics from Golgi to the apical plasma membrane and endogenously cycles through the rab 11a-myosin Vb recycling endosomal system. LKB1 knockout mice were jaundiced, lost weight and manifested impaired bile canalicular formation and intracellular trafficking of ABCB11, and died within three weeks. Using live cell imaging, fluorescence recovery after photobleaching (FRAP), particle tracking, and biochemistry, we found that LKB1 activity is required for microtubule-dependent trafficking of ABCB11 to the canalicular membrane. In control hepatocytes, ABCB11 trafficking was accelerated by taurocholate and cAMP; however, in LKB1 knockout hepatocytes, ABCB11 trafficking to the apical membrane was greatly reduced and restored only by cAMP, but not taurocholate. cAMP acted through a PKA-mediated pathway which did not activate AMPK. Our studies establish a regulatory role for LKB1 in ABCB11 trafficking to the canalicular membrane, hepatocyte polarization, and canalicular network formation.

}, keywords = {AMP-Activated Protein Kinases, Animals, ATP-Binding Cassette Transporters, Bile Acids and Salts, Cell Membrane, Cell Polarity, Cyclic AMP, Cyclic AMP-Dependent Protein Kinases, Endosomes, Gene Expression Regulation, Golgi Apparatus, Hepatocytes, Mice, Mice, Knockout, Myosin Type V, Primary Cell Culture, Protein Transport, Protein-Serine-Threonine Kinases, rab GTP-Binding Proteins, Signal Transduction, Taurocholic Acid}, issn = {1932-6203}, doi = {10.1371/journal.pone.0091921}, author = {Homolya, L{\'a}szl{\'o} and Fu, Dong and Sengupta, Prabuddha and Jarnik, Michal and Gillet, Jean-Pierre and Vitale-Cross, Lynn and Gutkind, J Silvio and Lippincott-Schwartz, Jennifer and Arias, Irwin M} } @article {47684, title = {Lipids and cholesterol as regulators of traffic in the endomembrane system.}, journal = {Annual review of biophysics}, volume = {39}, year = {2010}, month = {2010}, pages = {559-78}, abstract = {

The endomembrane system of eukaryotic cells uses membrane-enclosed carriers to move diverse macromolecules among different membrane-bound compartments, a requirement for cells to secrete and take up molecules from their environment. Two recycling pathways-biosynthetic and endocytic, each with specific lipid components-make up this system, with the Golgi apparatus mediating transport between the two. Here, we integrate lipid-based mechanisms into the description of this system. A partitioning model of the Golgi apparatus is discussed as a working hypothesis to explain how membrane lipids and proteins that are segregated based on lateral lipid partitioning support the unique composition of the biosynthetic and endocytic recycling pathways in the face of constant trafficking of molecular constituents. We further discuss how computational modeling can allow for interpretation of experimental findings and provide mechanistic insight into these important cellular pathways.

}, keywords = {Animals, Bacteria, Cholesterol, Endocytosis, Golgi Apparatus, Humans, Intracellular Membranes, Lipid Metabolism, Protein Transport}, issn = {1936-1238}, doi = {10.1146/annurev.biophys.093008.131357}, author = {Lippincott-Schwartz, Jennifer and Phair, Robert D} } @article {47677, title = {The long road: peering into live cells.}, journal = {Nature cell biology}, volume = {12}, year = {2010}, month = {2010 Oct}, pages = {918}, keywords = {Cell Biology, Cell Survival, Green Fluorescent Proteins, History, 20th Century, History, 21st Century, Microscopy, Fluorescence, Photobleaching, Protein Transport, Research Personnel}, issn = {1476-4679}, doi = {10.1038/ncb1010-918}, author = {Lippincott-Schwartz, Jennifer} }