Bag Research Group

RESEARCH

Research in our laboratory aims to understand the physical chemistry principles governing plasma membrane associated biological processes in live cells. We apply a wide range of biophysical techniques, especially spatially and temporally resolved fluorescence microscopy and spectroscopy, available in our department and at the central research facility, IIT Kharagpur. We also develop novel fluorescence-based analytical techniques and data analysis routines. Our current research thrusts are briefly described below.

NANOSCALE DYNAMICS AND ORGANIZATION OF PLASMA MEMBRANES

Plasma membranes of live cell are highly heterogenous due to simultaneous interactions between thousands of chemically diverse membrane constituents among themselves as well as with the adjacent cellular components. These dynamic, reversible, and sometimes energy (ATP)-dependent soft interactions give rise to an out-of-equilibrium plasma membrane steady-state exhibiting some unique biophysical features. Example of a unique structural feature of membrane is short-lived, nanoscale membrane regions resembling features of liquid ordered (Lo) phase which is at a fluid state but more ordered than the surrounding liquid disordered (Ld) regions. We systematically investigate biophysical and biochemical origin and lifetime of this 2D, Lo-like phase, sometimes dubbed as membrane rafts or nanodomains, in plasma membranes using a combinatorial top-down and bottom-up approaches and advanced single molecule sensitive fluorescence spectroscopy and microscopy.

TRANSMEMBRANE RECEPTOR SIGNALING

The functions of cell surface receptors, which are 'solvated' in the plasma membrane, depend on their ability to recognize extracellular signals (in form of chemical, mechanical, and other types of cues) and transmit that across plasma membrane for intracellular processing required for proper cellular decision making. Recently, it is emerging that the biophysical properties of plasma membranes play decisive roles in stimulated transmembrane signaling. We are currently working on the molecular level understanding of stimulated transmembrane signaling via epidermal growth factor receptor (EGFR) and an immunoreceptor system related to allergy response especially on the importance of membrane lipids in these processes. We use advanced fluorescence microscopy and molecular biology techniques in these investigations.

BIOPHYSICS OF EXTRACELLULAR VESICLES

Extracellular vesicles (EVs), as the name suggests, are vesicles shed by living cells in the extracellular space. In addition to other biological functions, EVs generally act as novel cargoes for cell-to-cell communications. They are believed to carry genetic materials from the host cells to nearby receiving cells for easy and rapid transmission of cellular information. Different kinds of EVs, including microvesicles and exosomes, are likely to have different biological functions. We are investigating the fine differences in the biogenesis and mechanical properties of various types of EVs freshly isolated from cells in culture. We are using prostate cancer as a model system to understand the mode of action of EVs in orchestrated cell-to-cell communication required for rapid proliferation of cancer cells. We majorly use high-speed ultracentrifugation, fluorescence microscopy, and force microscopy in this project.