Optical tools have unparalleled spatial and temporal precision and have been instrumental to better understand various processes in modern medicine and biology. The overall goal of my research laboratory is to understand the laser-plasmonic nanoparticle interactions and its effects at the interface between biological systems and nanomaterials. Specifically, experimental techniques and methods have been developed to understand the effects of nanoparticle plasmonic heating on proteins and lipids immediately next to the nanoparticle. This has led to new enabling tools for optical protein manipulation and photosensitive nanovesicles for molecular uncaging, as well as innovative diagnostic methods. This proposed research focus on the development of optical control of protein activity in live cells, namely plasmon-assisted light inactivation (PALI). PALI is based on pulsed laser heating (nanosecond) of plasmonic nanoparticles, and its thermally confined heating to unfold and denature surrounding proteins within a few nanometers of nanoparticle surface. Thus, PALI also effectively acts a unique nano temperature-jump (T-jump), an innovative experimental platform to address a gap for protein unfolding investigations. In the next five years, I plan to develop my research program in these two directions. Firstly, I will focus on developing this new optical tool to manipulate protein activity in live cells with emphasis on G-protein coupled receptors (GPCR), an important and diverse class of membrane receptors that mediate extracellular to intracellular signaling. This encompasses a systematic approach to understand the interaction and trafficking of nanoparticles with GPCR, the cellular responses of PALI on GPCR signaling, and finally the applicability of PALI on other GPCRs. I will primarily use a specific GPCR, protease activated receptor 2 (PAR2) that is important for chronic pain, as a working model. To test for other GPCRs, I will test GPCRs for neuropeptides, which are synergistic with our efforts to create neuropeptide photosensitive nanovesicles. Secondly, I will concentrate on the characterization of the nano T-jump by addressing two fundamental questions: (1) can the nanoparticle temperature be directly measured during pulsed laser heating or after a short delay? (2) How does the protein unfold under nano T-jump? These involves our existing collaborations with the Argonne National Lab to probe the gold lattice expansion using advanced spectroscopy, and various structural and functional assays to measure the protein unfolding and inactivation due to the nano T-jump. By the end of the five years, I anticipate solving important technical challenges to demonstrate the use of PALI to manipulate protein activity in live cells through GPCRs, and obtain a clear understanding of the temperature history and protein responses with the innovative nano T-jump platform. These outcomes would generate interest to the broad research community and enable others to tackle important challenges in cell biology using PALI.
Proteins are important building blocks of biological systems and optical control of protein activity offers insights in its function at precise time and locations. This work focuses on developing a novel optical method to control protein activity in live cells by using short laser pulses and tiny nanoparticles. Success of this proposed work overcomes important limitations of current approaches and enables a new experimental platform to study protein conformation changes.
