New study explores cell receptors crucial to cardiovascular health

Cardiovascular diseases remain one of the main causes of death in the world. One of the major contributors to these conditions is high blood pressure or hypertension.

Although treatments exist for the condition, which affects For tens of millions of Americans, these remedies are not without side effects, and some variants of the disease are resistant to treatment. The need for more effective therapies to treat hypertension-related diseases is therefore acute. The illustration shows a portion of the pGC-A receptor, known as the extracellular domain, protruding from cell surfaces in the cardiovascular system. Small molecules bind to the receptor and exert subtle control over blood pressure. The new research offers the first glimpse of the full-length receptor, a vital step in the development of new drugs to treat hypertension and other conditions.

However, for this To do so, biologists need more detailed maps of the mechanisms underlying cardiovascular regulation. One of these regulators is a protein receptor located at the top of cardiovascular cells, acting as a conduit for messages that are transmitted when specific hormone molecules bind to them.

Known as pGC-A, this membrane receptor acts much like a thermostat, sensitively adjusting the body’s blood pressure to maintain a homeostatic balance essential for health. The receptor not only acts as an important cellular component for vascular and cardiac homeostasis, but also plays a vital role in lipid metabolism and is implicated in the development of cancer.

In a new study, published in the current issue of the journal Scientific Reports, researchers from the Biodesign Center for Used Structural Discovery at Arizona State University and their colleagues, in collaboration with the Mayo Clinic, Rochester, make critical progress towards unveiling the framework of pGC-A.

The study provides the first purification, characterization and preliminary structural analysis of the full-length protein receptor. Research advances include the crystallization of the protein and the demonstration that these crystals diffract X-rays – two critical steps essential to solving the construct.

A better understanding of this complex receptor and its signaling mechanisms paves the way for a new series of antihypertensive drugs, which could help ward off heart attacks and strokes and improve recovery after these incidents.

“This achievement is the first X-ray diffraction described for a new class of membrane protein receptors, and represents a further effort extraordinary hard work from our graduate student, Shangji Zhang,” said Debbie Hansen, co-author and biodesign researcher. “Unique lesson constructs of membrane proteins often require years of effort and rely on similar critical advances.”

Department co-author John C. Burnett Jr. of Cardiovascular Medicine, Mayo Clinic, Rochester, worked on the development of candidate molecules for new antihypertensive drugs, based on the structure of the pGC-A receptor.

Breathtaking Threat

According to the Organization world health, more than a third of all deaths worldwide can be attributed to cardiovascular disease. Hypertension is one of the major contributing factors to the progression of cardiovascular disease.

The burden of hypertension has been steadily increasing, resulting in a recent recommendation from the National Heart, Lung, and Blood Institute’s Hypertension Task Force to “develop new drugs and treatments to target diverse populations of hypertensive patients, such as those with resistant hypertension.” ”

Treatment-resistant forms of hypertension, more likely to occur in people who are obese, diabetic or with renal insufficiency, represent 12 at 15 % of hypertensive patients. Such individuals show a limited or poor response to existing therapies. Ailment can develop when blood vessels become calcified and inelastic, losing their ability to fully contract and relax. Clinical studies show that treating high blood pressure reduces the risk of stroke from 35 to 40% and the risk of heart failure of 50 %.

Cardiovascular disease includes rheumatic heart disease and congenital coronary heart disease , cerebral and peripheral arterial deep vein thrombosis and pulmonary embolism. Coronary artery disease, one of the main causes of death, occurs when blood flow to heart muscle cells is reduced or obstructed, which can lead to heart failure. In the United States alone, the situation should increase to 50 billion dollars by 11357.

New ideas begin to crystallize

The pGC-A membrane receptor exists in three primary forms. This class of receptors is so large that it comprises the majority of pharmaceutical drug targets. For most organisms, whether they are prokaryotes like bacteria or eukaryotes like mammals, 20 to 30 % of the genome is devoted to the expression of membrane proteins. These receptors protrude from the outer cell membrane and penetrate deep inside the cell, often acting as conduits for external signals that alter the cell’s behavior.

However , designing drugs to target membrane proteins requires a very detailed blueprint of the receptor structure, usually with atomic-scale resolution. Using this information, drug designers can design a drug that binds selectively and precisely with the cellular receptor, to produce a given result.

In the case of pGC -A, binding molecules are peptide hormones produced by cells of the cardiovascular system. Known as natriuretic peptide hormones, they occur in natural variations and can also be engineered synthetically, using genetic mutation. Part of the receptor’s activity involves the conversion of GTP to cGMP, a molecule essential for the normal functioning of vital organs.

“The heart is not just a pump, but an endocrine gland that produces a very beneficial hormone called atrial natriuretic peptide (ANP),” says Burnett. “This hormone plays an essential role in blood pressure, kidneys and overall metabolic balance.”

Dig deeper

To date, only the extracellular component of the pGC-A receptor has been characterized. The current work is a major step towards characterizing the full-length framework, in particular the transmembrane domain and functional regions of the intracellular domain, about which little is currently known.

To achieve this, the researchers use a method known as baculovirus protein expression. The process involves turning insect cells into tiny protein-producing factories. Insect cells resemble human cells in terms of protein processing machinery, but are easier and cheaper to culture than mammalian cells. Baculovirus vectors allow researchers to turn an insect virus into a vehicle to deliver the genetic recipe for a protein.

The process involves inserting a gene to make the receptor in a special type of vector or DNA guide known as a bacmid. The recombinant bacmid carrying the receptor gene is then used to infect insect cells, which begin to make recombinant baculoviruses.

The pGC-A receptor protein can then be extracted , purified and subjected to X-ray crystallography, to determine its composition. The process is delicate, laborious and prone to failure for various reasons. Only a small number of the many existing membrane proteins have been fully characterized, making the preliminary characterization of pGC-A an impressive achievement.

The cell expression system of insects offers several advantages for protein expression, particularly in the case of membrane proteins like pGC-A. The technique allows researchers to more easily extract correctly folded membrane proteins directly from the cell membrane, compared to bacterial expression of common misfolded and non-functional proteins with traditional expression in Escherichia coli (E. coli).

Horizon line

“It was an enormous achievement,” said Hansen. “Membrane proteins are not trivial to purify, and she was also able to achieve protein crystallization and X-ray diffraction.”

Further purification and better diffraction data will ultimately enable structural characterization at the atomic level.

Research opens the door to detailed characterization of other membrane proteins, which could eventually end up in drugs effective in controlling hypertension and a wide range of other medical conditions.

“A major goal is to develop breakthrough drugs based on ANP and its target receptor in man to treat high blood pressure, heart failure as well as obesity,” Burnett said. “The work done by the ASU and Mayo teams and reported in Scientific Reviews is helping to crack the magic formula of the receptor target and will accelerate the development of new drugs and truly help customers around the world.”

Petra Fromme, director of the Heart for Utilized Structural Discovery, who is the lead author of this study and served as Zhang’s thesis supervisor, is excited about the high impact of this work.

“Metabolic diseases are one of the most significant health threats in the 21 century, with diabetes, high blood pressure and heart disease killing millions of people each year – and the numbers are rising. Work on the pGC-A receptor has the potential to develop an effective drug that reduces symptoms without serious side effects,” she said.

This project was supported by an award to JCB and PF from the Mayo/ASU Structural Biology Alliance and the Biodesign Center for Utilized Structural Discovery at Arizona Condition University. a US Department of Energy (DOE) Office of Science User Setup operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357.

The research was carried out with the generous assistance of the Center Biodesign for innovations in e-medicine t from the Custom Diagnosis Center.

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