@article {1135, title = {Spoiled for Choice: Diverse Endocytic Pathways Function at the Cell Surface [BLiSC - NCBS, inStem, C-CAMP]}, journal = {Annu Rev Cell Dev Biol}, year = {2019}, month = {2019 Jul 05}, abstract = {

Endocytosis has long been identified as a key cellular process involved in bringing in nutrients, in clearing cellular debris in tissue, in the regulation of signaling, and in maintaining cell membrane compositional homeostasis. While clathrin-mediated endocytosis has been most extensively studied, a number of clathrin-independent endocytic pathways are continuing to be delineated. Here we provide a current survey of the different types of endocytic pathways available at the cell surface and discuss a new classification and plausible molecular mechanisms for some of the less characterized pathways. Along with an evolutionary perspective of the origins of some of these pathways, we provide an appreciation of the distinct roles that these pathways play in various aspects of cellular physiology, including the control of signaling and membrane tension. Expected final online publication date for the Volume 35 is October 7, 2019. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

}, issn = {1530-8995}, doi = {10.1146/annurev-cellbio-100617-062710}, author = {Thottacherry, Joseph Jose and Sathe, Mugdha and Prabhakara, Chaitra and Mayor, Satyajit} } @article {1015, title = {Mechanochemical feedback control of dynamin independent endocytosis modulates membrane tension in adherent cells. [Microfluidics and Microfabrication Facility (INT)]}, journal = {Nat Commun}, volume = {9}, year = {2018}, month = {2018 10 11}, pages = {4217}, abstract = {

Plasma membrane tension regulates many key cellular processes. It is modulated by, and can modulate, membrane trafficking. However, the cellular pathway(s) involved in this interplay is poorly understood. Here we find that, among a number of endocytic processes operating simultaneously at the cell surface, a dynamin independent pathway, the CLIC/GEEC (CG) pathway, is rapidly and specifically upregulated upon a sudden reduction of tension. Moreover, inhibition (activation) of the CG pathway results in lower (higher) membrane tension. However, alteration in membrane tension does not directly modulate CG endocytosis. This requires vinculin, a mechano-transducer recruited to focal adhesion in adherent cells. Vinculin acts by controlling the levels of a key regulator of the CG pathway, GBF1, at the plasma membrane. Thus, the CG pathway directly regulates membrane tension and is in turn controlled via a mechano-chemical feedback inhibition, potentially leading to homeostatic regulation of membrane tension in adherent cells.

}, keywords = {Animals, Biomechanical Phenomena, Cell Adhesion, Cell Membrane, Dynamins, Endocytosis, Feedback, Physiological, Mechanotransduction, Cellular, Mice, Signal Transduction, Temperature, Vinculin}, issn = {2041-1723}, doi = {10.1038/s41467-018-06738-5}, author = {Thottacherry, Joseph Jose and Kosmalska, Anita Joanna and Kumar, Amit and Vishen, Amit Singh and Elosegui-Artola, Alberto and Pradhan, Susav and Sharma, Sumit and Singh, Parvinder P and Guadamillas, Marta C and Chaudhary, Natasha and Vishwakarma, Ram and Trepat, Xavier and Del Pozo, Miguel A and Parton, Robert G and Rao, Madan and Pullarkat, Pramod and Roca-Cusachs, Pere and Mayor, Satyajit} } @article {507, title = {Tailor-made ezrin actin binding domain to probe its interaction with actin in-vitro. [Protein Technology Core]}, journal = {PLoS One}, volume = {10}, year = {2015}, month = {2015}, pages = {e0123428}, abstract = {

Ezrin, a member of the ERM (Ezrin/Radixin/Moesin) protein family, is an Actin-plasma membrane linker protein mediating cellular integrity and function. In-vivo study of such interactions is a complex task due to the presence of a large number of endogenous binding partners for both Ezrin and Actin. Further, C-terminal actin binding capacity of the full length Ezrin is naturally shielded by its N-terminal, and only rendered active in the presence of Phosphatidylinositol bisphosphate (PIP2) or phosphorylation at the C-terminal threonine. Here, we demonstrate a strategy for the design, expression and purification of constructs, combining the Ezrin C-terminal actin binding domain, with functional elements such as fusion tags and fluorescence tags to facilitate purification and fluorescence microscopy based studies. For the first time, internal His tag was employed for purification of Ezrin actin binding domain based on in-silico modeling. The functionality (Ezrin-actin interaction) of these constructs was successfully demonstrated by using Total Internal Reflection Fluorescence Microscopy. This design can be extended to other members of the ERM family as well.

}, keywords = {Actins, Animals, Avian Proteins, Chickens, Cytoskeletal Proteins, In Vitro Techniques, Microfilament Proteins, Models, Molecular, Protein Interaction Domains and Motifs, Recombinant Fusion Proteins}, issn = {1932-6203}, doi = {10.1371/journal.pone.0123428}, author = {Shrivastava, Rohini and K{\"o}ster, Darius and Kalme, Sheetal and Mayor, Satyajit and Neerathilingam, Muniasamy} } @article {1010, title = {Light driven ultrafast electron transfer in oxidative redding of Green Fluorescent Proteins. [Protein Technology Facility]}, journal = {Sci Rep}, volume = {3}, year = {2013}, month = {2013}, pages = {1580}, abstract = {

Fluorescent proteins undergoing green to red (G/R) photoconversion have proved to be potential tools for investigating dynamic processes in living cells and for photo-localization nanoscopy. However, the photochemical reaction during light induced G/R photoconversion of fluorescent proteins remains unclear. Here we report the direct observation of ultrafast time-resolved electron transfer (ET) during the photoexcitation of the fluorescent proteins EGFP and mEos2 in presence of electron acceptor, p-benzoquinone (BQ). Our results show that in the excited state, the neutral EGFP chromophore accepts electrons from an anionic electron donor, Glu222, and G/R photoconversion is facilitated by ET to nearby electron acceptors. By contrast, mEos2 fails to produce the red emitting state in the presence of BQ; ET depletes the excited state configuration en route to the red-emitting fluorophore. These results show that ultrafast ET plays a pivotal role in multiple photoconversion mechanisms and provide a method to modulate the G/R photoconversion process.

}, keywords = {Benzoquinones, Electron Transport, Green Fluorescent Proteins, Light, Oxidation-Reduction}, issn = {2045-2322}, doi = {10.1038/srep01580}, author = {Saha, Ranajay and Verma, Pramod Kumar and Rakshit, Surajit and Saha, Suvrajit and Mayor, Satyajit and Pal, Samir Kumar} } @article {713, title = {Active remodeling of cortical actin regulates spatiotemporal organization of cell surface molecules.}, journal = {Cell}, volume = {149}, year = {2012}, month = {2012 Jun 08}, pages = {1353-67}, abstract = {

Many lipid-tethered proteins and glycolipids exist as monomers and nanoclusters on the surface of living cells. The spatial distribution and dynamics of formation and breakup of nanoclusters does not reflect thermal and chemical equilibrium and is controlled by active remodeling of the underlying cortical actin. We propose a model for nanoclustering based on active hydrodynamics, wherein cell surface molecules bound to dynamic actin are actively driven to form transient clusters. This consistently explains all of our experimental observations. Using FCS and TIRF microscopy, we provide evidence for the existence of short, dynamic, polymerizing actin filaments at the cortex, a key assumption of the theoretical framework. Our theory predicts that lipid-anchored proteins that interact with dynamic actin must exhibit anomalous concentration fluctuations, and a cell membrane protein capable of binding directly to actin can form nanoclusters. These we confirm experimentally, providing an active mechanism for molecular organization and its spatiotemporal regulation on the plasma membrane.

}, keywords = {Actins, Animals, Cell Line, Tumor, Cell Membrane, CHO Cells, Cricetinae, Cytoskeleton, Humans, Membrane Proteins, Models, Biological, Spectrometry, Fluorescence}, issn = {1097-4172}, doi = {10.1016/j.cell.2012.05.008}, author = {Gowrishankar, Kripa and Ghosh, Subhasri and Saha, Suvrajit and C, Rumamol and Mayor, Satyajit and Rao, Madan} } @article {715, title = {Dynamic imaging of homo-FRET in live cells by fluorescence anisotropy microscopy.}, journal = {Methods Enzymol}, volume = {505}, year = {2012}, month = {2012}, pages = {291-327}, abstract = {

Multiple lipid and protein components of the plasma membrane of a living cell are organized, both compositionally and functionally, at different spatial and temporal scales. For instance, Rab protein domains in membranes the clathrin-coated pit, or the immunological synapse are exquisite examples of functional compartmentalization in cell membranes. These assemblies consist in part of nanoscale complexes of lipids and proteins and are necessary to facilitate some specific sorting and signaling functions. It is evident that cellular functions require a regulated spatiotemporal organization of components at the nanoscale, often comprising of countable number of molecular species. Here, we describe multiple homo-FRET-based imaging methods that provide information about nanoscale interactions between fluorescently tagged molecules in live cells, at optically resolved spatial resolution.

}, keywords = {Animals, Cell Membrane, Cell Tracking, Drosophila, Fluorescence Polarization, Fluorescence Resonance Energy Transfer, Green Fluorescent Proteins, Image Processing, Computer-Assisted, Lipid Metabolism, Microscopy, Confocal, Microscopy, Fluorescence}, issn = {1557-7988}, doi = {10.1016/B978-0-12-388448-0.00024-3}, author = {Ghosh, Subhasri and Saha, Suvrajit and Goswami, Debanjan and Bilgrami, Sameera and Mayor, Satyajit} }