Scientists led by a team at the Medical Research Council (MRC) Mitochondrial Biology Unit, University of Cambridge, have worked out how a molecular machine found in mitochondria—the “powerhouses” of our cells—allows us to make the fuel we need from sugars, a process vital to all life on Earth.
The researchers identified the structure of this machine, the mitochondrial pyruvate carrier (MPC), and 50 years since its discovery, have shown how it operates like the lock on a canal to transport pyruvate, a molecule generated in the body from the breakdown of sugars, into mitochondria.
The MPC was first proposed to exist in 1971 and represents a potential drug target for treating disorders ranging from cancers and diabetes to neurodegeneration. The MRC scientists have now been able to visualise the structure of the MPC at the atomic scale using cryo-electron microscopy, a technique used to magnify an image of an object to around 165,000 times its real size. The team also provided the structures of different classes of inhibitor interacting with the same binding site on the human MPC molecule.
Maximilian Sichrovsky, a PhD student at Hughes Hall said, “Getting pyruvate into our mitochondria sounds straightforward, but until now we haven’t been able to understand the mechanism of how this process occurs. Using state-of-the-art cryo-electron microscopy, we’ve been able to show not only what this transporter looks like, but exactly how it works. It’s an extremely important process, and understanding it could lead to new treatments for a range of different conditions.”
Sichrovsky is co-first author of the team’s published paper in Science Advances, titled “Molecular basis of pyruvate transport and inhibition of the human mitochondrial pyruvate carrier.” In their report, the team concluded, “Here, we provide structures of the human MPC in the outward-open and inward-open configurations, unliganded or liganded with three different classes of inhibitors.”
Sugars in our diet provide energy for our bodies to function, explained co-author Sotiria Tavoulari, PhD, a senior research associate at the University of Cambridge. “When they are broken down inside our cells they produce pyruvate, but to get the most out of this molecule it needs to be transferred inside the cell’s powerhouses, the mitochondria. There, it helps increase 15-fold the energy produced in the form of the cellular fuel ATP.”
It was originally believed that pyruvate could enter mitochondria via diffusion, the authors noted. “However, pyruvate transport was shown to follow saturation kinetics, to be sensitive to sulfhydryl reagents, and to be abolished by small-molecule inhibitors, supporting the existence of a carrier protein, although its molecular identity was not discovered for several decades.”
Mitochondria are surrounded by two membranes. Pyruvate can easily pass through the outer of the two, but the inner membrane is impermeable to pyruvate. In 2012, scientists identified the proteins responsible for pyruvate transport in the mitochondria of yeast, flies, and humans, and it was shown that MPC consists of two small homologous membrane proteins that form heterocomplexes. “The mitochondrial pyruvate carrier (MPC) is responsible for transporting pyruvate, produced from sugars by glycolysis in the cytosol, into the mitochondrial matrix,” the authors explained. “This key transport step links cytosolic glycolysis with mitochondrial oxidative phosphorylation, increasing the adenosine 5′-triphosphate (ATP) yield by 15-fold.”
The newly reported work demonstrated that MPC operates via what they described as an “alternating access rocker-switch mechanism.” To transport pyruvate into the mitochondrion, first an outer “gate” of the carrier opens, allowing pyruvate to enter the carrier. This gate then closes, and the inner gate opens, allowing the molecule to pass through into the mitochondrion. “It works like the locks on a canal but on the molecular scale,” said co-corresponding author Edmund Kunji, PhD, professor at the MRC Mitochondrial Biology Unit, and a fellow at Trinity Hall, Cambridge. “There, a gate opens at one end, allowing the boat to enter. It then closes and the gate at the opposite end opens to allow the boat smooth transit through.”
Because of its central role in controlling the way mitochondria operate to produce energy, this carrier is now recognised as a promising drug target for a range of conditions, including diabetes, fatty liver disease, Parkinson’s disease, specific cancers, and even hair loss. “The mechanism of transport inhibition is of great interest, as MPC is being investigated as a drug target for a range of conditions,” the authors wrote.
The team’s newly reported study also determined the binding poses of three chemically distinct inhibitor classes. “We also solve the structures of MPC in inhibited states with three inhibitor classes, showing that they all exploit the same binding site, although all of the chemical groups are different,” they wrote. Kunji added, “Drugs inhibiting the function of the carrier can remodel how mitochondria work, which can be beneficial in certain conditions. Electron microscopy allows us to visualise exactly how these drugs bind inside the carrier to jam it—a spanner in the works, you could say. This creates new opportunities for structure-based drug design in order to develop better, more targeted drugs. This will be a real game changer.”
Pyruvate is not the only energy source available to us. Cells can also take their energy from fats stored in the body or from amino acids in proteins. Blocking the pyruvate carrier would force the body to look elsewhere for its fuel, creating opportunities to treat a number of diseases. In fatty liver disease, for example, blocking access to pyruvate entry into mitochondria could encourage the body to use potentially dangerous fat that has been stored in liver cells.
Likewise, there are certain tumour cells that rely on pyruvate metabolism, such as in some types of prostate cancer. These cancers tend to be very “hungry,” producing excess pyruvate transport carriers to ensure they can feed more. Blocking the carrier could then starve these cancer cells of the energy they need to survive, killing them.
Previous studies have also suggested that inhibiting the mitochondrial pyruvate carrier may reverse hair loss. Activation of human follicle cells, which are responsible for hair growth, relies on metabolism and, in particular, the generation of lactate. When the mitochondrial pyruvate carrier is blocked from entering the mitochondria in these cells, it is instead converted to lactate.
In their paper, the team concluded that revealing the binding poses of three major inhibitor classes will allow “… further exploration of MPC as a drug target for treating diabetes mellitus, specific cancers, metabolic dysfunction-associated steatotic liver disease, and neurodegeneration.”
The post Structure of Mitochondrial Pyruvate Carrier Drug Target Bound to Inhibitors Revealed appeared first on GEN - Genetic Engineering and Biotechnology News.
The researchers identified the structure of this machine, the mitochondrial pyruvate carrier (MPC), and 50 years since its discovery, have shown how it operates like the lock on a canal to transport pyruvate, a molecule generated in the body from the breakdown of sugars, into mitochondria.
The MPC was first proposed to exist in 1971 and represents a potential drug target for treating disorders ranging from cancers and diabetes to neurodegeneration. The MRC scientists have now been able to visualise the structure of the MPC at the atomic scale using cryo-electron microscopy, a technique used to magnify an image of an object to around 165,000 times its real size. The team also provided the structures of different classes of inhibitor interacting with the same binding site on the human MPC molecule.
Maximilian Sichrovsky, a PhD student at Hughes Hall said, “Getting pyruvate into our mitochondria sounds straightforward, but until now we haven’t been able to understand the mechanism of how this process occurs. Using state-of-the-art cryo-electron microscopy, we’ve been able to show not only what this transporter looks like, but exactly how it works. It’s an extremely important process, and understanding it could lead to new treatments for a range of different conditions.”
Sichrovsky is co-first author of the team’s published paper in Science Advances, titled “Molecular basis of pyruvate transport and inhibition of the human mitochondrial pyruvate carrier.” In their report, the team concluded, “Here, we provide structures of the human MPC in the outward-open and inward-open configurations, unliganded or liganded with three different classes of inhibitors.”
Sugars in our diet provide energy for our bodies to function, explained co-author Sotiria Tavoulari, PhD, a senior research associate at the University of Cambridge. “When they are broken down inside our cells they produce pyruvate, but to get the most out of this molecule it needs to be transferred inside the cell’s powerhouses, the mitochondria. There, it helps increase 15-fold the energy produced in the form of the cellular fuel ATP.”
It was originally believed that pyruvate could enter mitochondria via diffusion, the authors noted. “However, pyruvate transport was shown to follow saturation kinetics, to be sensitive to sulfhydryl reagents, and to be abolished by small-molecule inhibitors, supporting the existence of a carrier protein, although its molecular identity was not discovered for several decades.”
Mitochondria are surrounded by two membranes. Pyruvate can easily pass through the outer of the two, but the inner membrane is impermeable to pyruvate. In 2012, scientists identified the proteins responsible for pyruvate transport in the mitochondria of yeast, flies, and humans, and it was shown that MPC consists of two small homologous membrane proteins that form heterocomplexes. “The mitochondrial pyruvate carrier (MPC) is responsible for transporting pyruvate, produced from sugars by glycolysis in the cytosol, into the mitochondrial matrix,” the authors explained. “This key transport step links cytosolic glycolysis with mitochondrial oxidative phosphorylation, increasing the adenosine 5′-triphosphate (ATP) yield by 15-fold.”
The newly reported work demonstrated that MPC operates via what they described as an “alternating access rocker-switch mechanism.” To transport pyruvate into the mitochondrion, first an outer “gate” of the carrier opens, allowing pyruvate to enter the carrier. This gate then closes, and the inner gate opens, allowing the molecule to pass through into the mitochondrion. “It works like the locks on a canal but on the molecular scale,” said co-corresponding author Edmund Kunji, PhD, professor at the MRC Mitochondrial Biology Unit, and a fellow at Trinity Hall, Cambridge. “There, a gate opens at one end, allowing the boat to enter. It then closes and the gate at the opposite end opens to allow the boat smooth transit through.”
Because of its central role in controlling the way mitochondria operate to produce energy, this carrier is now recognised as a promising drug target for a range of conditions, including diabetes, fatty liver disease, Parkinson’s disease, specific cancers, and even hair loss. “The mechanism of transport inhibition is of great interest, as MPC is being investigated as a drug target for a range of conditions,” the authors wrote.
The team’s newly reported study also determined the binding poses of three chemically distinct inhibitor classes. “We also solve the structures of MPC in inhibited states with three inhibitor classes, showing that they all exploit the same binding site, although all of the chemical groups are different,” they wrote. Kunji added, “Drugs inhibiting the function of the carrier can remodel how mitochondria work, which can be beneficial in certain conditions. Electron microscopy allows us to visualise exactly how these drugs bind inside the carrier to jam it—a spanner in the works, you could say. This creates new opportunities for structure-based drug design in order to develop better, more targeted drugs. This will be a real game changer.”
Pyruvate is not the only energy source available to us. Cells can also take their energy from fats stored in the body or from amino acids in proteins. Blocking the pyruvate carrier would force the body to look elsewhere for its fuel, creating opportunities to treat a number of diseases. In fatty liver disease, for example, blocking access to pyruvate entry into mitochondria could encourage the body to use potentially dangerous fat that has been stored in liver cells.
Likewise, there are certain tumour cells that rely on pyruvate metabolism, such as in some types of prostate cancer. These cancers tend to be very “hungry,” producing excess pyruvate transport carriers to ensure they can feed more. Blocking the carrier could then starve these cancer cells of the energy they need to survive, killing them.
Previous studies have also suggested that inhibiting the mitochondrial pyruvate carrier may reverse hair loss. Activation of human follicle cells, which are responsible for hair growth, relies on metabolism and, in particular, the generation of lactate. When the mitochondrial pyruvate carrier is blocked from entering the mitochondria in these cells, it is instead converted to lactate.
In their paper, the team concluded that revealing the binding poses of three major inhibitor classes will allow “… further exploration of MPC as a drug target for treating diabetes mellitus, specific cancers, metabolic dysfunction-associated steatotic liver disease, and neurodegeneration.”
The post Structure of Mitochondrial Pyruvate Carrier Drug Target Bound to Inhibitors Revealed appeared first on GEN - Genetic Engineering and Biotechnology News.