Nihon Pharmaceutical University

Transcription

Shige Yoshimura, Ph.D. (Associate Prof.) in Laboratory of Plasma Membrane and Nuclear Signaling. Today, I would like to introduce our research projects and some of our recent research progresses. Our body is made of 'CELLs'. Cells are composed of water, protein, lipid, nucleic acid, sugar and minerals. Among these, protein is the most important molecule for maintaining the cell's life. Our body contains more than 20,000 different kinds of proteins. They must exert their proper functions at the right place and at the right timing, to build up our body and maintain our life. Our research group is trying to 'see' the shape of proteins and the process they work ,and understand the mechanism of how 'life' is maintained by these biomolecules. Protein is very small molecule. It is too small to be visualized by your eyes nor by conventional light microscopes. Can you imagine how small they are? The size of a single cell in our body is approximately several tens of micrometers (um). ; less than 1/10 of one millimeter. The size of a single protein is 1/10,000 of a cell; nanometer (nm), which is one millionth of 1 millimeter (mm). Now, if you assume that a single protein would be this baseball, a cell equals to our university campus, and your body becomes far larger than the earth. Now, you can imagine how small proteins are. Due to its small size, it is very hard to 'see' a single protein molecule by eyes or microscopes. It is just like you are trying to see this baseball in our campus from the outside of the earth! Our group is trying to understand the structure and the function of such cellular proteins by utilizing a special microscope, various kinds of spectroscopic methods and recent computer simulation methods. How to 'see' proteins Masahiro Kumeta (Assistant Professor) I will explain how we 'see' a single protein molecule. Here we have a special type of microscope, Atomic Force Microscope (AFM). AFM visualizes the shape of the molecule on a flat substrate by scaning its surface by a sharp tip. Because of such a wide range of resolution, we can observe various biomolecules such as cell, chromosome, nucleosome, and down to single protein and DNA molecule, ,as well as molecular process of how proteins assomble into and disassemble from a large complex. One of the significant advantages of AFM is its ability to observe vaious biomolecules in liquid. This movie shows the action of an enzyme (restriction enzyme) digesting DNA double strand in liquid. It is really exciting to actually observe such a small molecular world event, isn't it? We are trying to uncover molecular worlds by AFM and other nano-technologies. The following are the articles we have published recently. stress on a cell The next story is related to 'stress'. I guess you sometimes fell stresses in a dairy life. Cells are also feeling various stresses from the environment. When cell are exposed to ultraviolet light (UV), heat, oxygen,chemical substances, and starvation , they responded and protect themselves from the stress. When cells are exposed to such stresses, they are able to change gene expression patterns in the nucleus and protect themselves from the stress. For example, cells turn on a specific set of genes to resist to the stress , and shut off genes which should be protected from the stress. Our research group recently reported that upon the oxidative stress, cells change the intracellular traffic system between the cytoplasm and the nucleus. Let's see more details. All of the cellular proteins are synthesized in the cytoplasm , and then delivered to the places they function. The proteins involved the gene regulation are also aynthesized in the cytoplasm and delivered to the nucleus. The 'nuclear pore' is the protein complex existing in the nuclear envelope and mediates the traffics between the cytoplasm and the nucleoplasm. Our group recently reported that when cells are exposed to the oxidative stress, the nuclear pore changes its structure, and reduces the traffic flow. We found that this is due to the increased number of covalent bonds called 'disulfide bond' among the sunbunits of the nuclear pore. If you are interested in, please access to the journal article shown here. We hope it is of interest to you. Proteins supporting the cell's architecture As mentioned before, there are several tens of thousands of different proteins in a cell. Can you imagine how many molecules of a certain kind protein exist in a signle cell? A recent research reported the average number of a certain kind of protein in a cell as about 50,000. However, the most abundant protein exists more than a hundred million molecules per cells, , while minor ones are less than a hundred. Can you imagine how much crowded the cytoplasm is? Let me make a rough estimation. Protein crowding in a cell is roughly same as the situation of 3-4 people in a telephone box! These proteins are dynamically associate and dissociate with appropriate partners. ,and support the proper progress of a variety of biological reactions. To understand the molecular basis of spatio-temporal regulation of such complexes, we focused on a set of biochemically-stable fraction of proteins ,and performed 1) AFM-based morphological, 2) proteomic, and 3) antibody-based molecular analyses. For more details, please refer to these articles.