Nature Communications\u00a0<\/em>in 2022, Young and colleagues reported that insulin receptor mobility might be relevant to diabetes.<\/p>\nKnowing that many cellular functions are altered in diabetes, the researchers considered the possibility that altered protein mobility might somehow affect many proteins in cells. To test this hypothesis, they studied proteins involved in a broad range of cellular functions, including MED1, a protein involved in gene expression; HP1\u03b1, a protein involved in gene silencing; FIB1, a protein involved in production of ribosomes; and SRSF2, a protein involved in splicing of messenger RNA. They used single-molecule tracking and other methods to measure how each of those proteins moves in healthy cells and in cells in disease states. All but one of the proteins showed reduced mobility (about 20-35%) in the disease cells.<\/p>\n
\u201cI\u2019m excited that we were able to transfer physics-based insight and methodology, which are commonly used to understand the single-molecule processes like gene transcription in normal cells, to a disease context and show that they can be used to uncover unexpected mechanisms of disease,\u201d Zheng says. \u201cThis work shows how the random walk of proteins in cells is linked to disease pathology.\u201d<\/p>\n
Moreno concurs: \u201cIn school, we\u2019re taught to consider changes in protein structure or DNA sequences when looking for causes of disease, but we\u2019ve demonstrated that those are not the only contributing factors. If you only consider a static picture of a protein or a cell, you miss out on discovering these changes that only appear when molecules are in motion.\u201d<\/p>\n
\u00a0Can\u2019t commute across the cell, I\u2019m all tied up right now<\/h2>\n Next, the researchers needed to determine what was causing the proteins to slow down. They suspected that the defect had to do with an increase in cells of the level of reactive oxygen species (ROS), molecules that are highly prone to interfering with other molecules and their chemical reactions. Many types of chronic-disease-associated triggers, such as higher sugar or fat levels, certain toxins, and inflammatory signals, lead to an increase in ROS, also known as an increase in oxidative stress. The researchers measured the mobility of the proteins again, in cells that had high levels of ROS and were not otherwise in a disease state, and saw comparable mobility defects, suggesting that oxidative stress was to blame for the protein mobility defect.<\/p>\n
The final part of the puzzle was why some, but not all, proteins slow down in the presence of ROS. SRSF2 was the only one of the proteins that was unaffected in the experiments, and it had one clear difference from the others: its surface did not contain any cysteines, an amino acid building block of many proteins. Cysteines are especially susceptible to interference from ROS because it will cause them to bond to other cysteines. When this bonding occurs between two protein molecules, it slows them down because the two proteins cannot move through the cell as quickly as either protein alone.<\/p>\n
About half of the proteins in our cells contain surface cysteines, so this single protein mobility defect can impact many different cellular pathways. This makes sense when one considers the diversity of dysfunctions that appear in cells of people with chronic diseases: dysfunctions in cell signaling, metabolic processes, gene expression and gene silencing, and more. All of these processes rely on the efficient functioning of proteins\u2014including the diverse proteins studied by the researchers. Young and colleagues performed several experiments to confirm that decreased protein mobility does in fact decrease a protein\u2019s function. For example, they found that when an insulin receptor experiences decreased mobility, it acts less efficiently on IRS1, a molecule to which it usually adds a phosphate group.<\/p>\n
From understanding a mechanism to treating a disease<\/h2>\n Discovering that decreased protein mobility in the presence of oxidative stress could be driving many of the symptoms of chronic disease provides opportunities to develop therapies to rescue protein mobility. In the course of their experiments, the researchers treated cells with an antioxidant drug\u2014something that reduces ROS\u2014called N-acetyl cysteine and saw that this partially restored protein mobility.<\/p>\n
The researchers are pursuing a variety of follow ups to this work, including the search for drugs that safely and efficiently reduce ROS and restore protein mobility. They developed an assay that can be used to screen drugs to see if they restore protein mobility by comparing each drug\u2019s effect on a simple biomarker with surface cysteines to one without. They are also looking into other diseases that may involve protein mobility, and are exploring the role of reduced protein mobility in aging.<\/p>\n
\u201cThe complex biology of chronic diseases has made it challenging to come up with effective therapeutic hypotheses,\u201d says Young, who is also a professor of biology at the Massachusetts Institute of Technology. \u201cThe discovery that diverse disease-associated stimuli all induce a common feature, proteolethargy, and that this feature could contribute to much of the dysregulation that we see in chronic disease, is something that I hope will be a real game changer for developing drugs that work across the spectrum of chronic diseases.\u201d<\/p>\n","protected":false},"excerpt":{"rendered":"
Chronic diseases like type 2 diabetes and inflammatory disorders have a huge impact on humanity. They are a leading cause of disease burden and deaths around the globe, are physically and economically taxing, and the number of people with such diseases is growing. Treating chronic disease has proven difficult because there is not one simple […]<\/p>\n","protected":false},"author":1783,"featured_media":30558,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[6240,6221],"tags":[],"class_list":["post-30557","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-whitehead-institute-faculty-locations","category-whitehead-institute","placement-placement-homepage","research-area-cancer-biology","research-area-human-disease","research-area-stem-cell-and-developmental-biology"],"acf":[],"yoast_head":"\n
Cellular traffic congestion in chronic diseases suggests new therapeutic targets - MIT Department of Biology<\/title>\n \n \n \n \n \n \n \n \n \n \n\t \n\t \n\t \n \n \n \n\t \n\t \n\t \n