An Interview with Professors Manuel and Ann Varela: Who was The Viscount Christian de Duve?

Apr 4, 2020 by

The Viscount Christian de Duve

Michael F. Shaughnessy –

1) One of the most fascinating scientists I have ever heard about was the Viscount de Duve- first of all, where was he born and where was he educated?

Nobel Laureate Dr. Christian René Marie de Duve is most famous amongst the biochemists and cell biologists for his discoveries of the organelles lysosome and peroxisome. De Duve was born on the second day of October in 1917 in Thames Ditton, Surrey, in the U.K. to parents Alphonse and Madeleine Pungs de Duve. Alphonse had been a real estate agent, and Christian’s parents had fled Belgium as war refugees shortly after the Great War started.

Early on as a child, Christian was recognized as gifted. He attended Onze-Lieve-Vrouwinstituut high school in Antwerp, where he was educated by teachers of the Jesuit Order, until his graduation in 1934. Then de Duve attended Catholic University at Leuven, where the student took his doctorate in medicine (M.D.) in 1941. He became a postdoctoral fellow working under Professor Hugo Theorell in Stockholm, Sweden. In 1945, Dr. de Duve took what is considered an equivalent of a Ph.D. degree for his studies on insulin, glucagon, and diabetes while at Catholic University. In 1946, he earned his master’s degree in chemistry.

2) Apparently, World War II interfered with his medical studies, and he was later taken prisoner by the Germans- but fled in what could only be called a precursor to the great Steven McQueen movie The Great Escape. What transpired exactly?

According to a 2013 publication in PLoS Biology, de Duve was serving as an officer in the medical corps in France when he was discovered by the Germans and taken prisoner of war. Unlike the unfortunate fiasco that occurred to the escapees in the film and its real-life victims in that incident, de Duve’s escape was successful.

As a medical student during World War II in 1940, de Duve had become interested in research, especially in the field of endocrinology. He thus began investigative work in the laboratory of Dr. Joseph P. Bouckaert.

Just prior to finishing his M.D., his medical studies were interrupted because of the Second World War in 1940. Instead, he was deployed for medical military service. Shortly after deployment, however, his regiment was captured in southern France by the invading German army.

While the precise details are sketchy and are perhaps lost to history, we do know, however, that he quickly managed to escape the confines of German captivity by talking. De Duve’s mastery of four languages helped him to cleverly elude recapture as he made good his complete freedom to Belgium. He communicated his way through checkpoints during his perilous journey by convincingly speaking German and Flemish. In later years, he was to describe this adventure as being somewhat more comical in nature, as opposed to a heroic one.

Once back to safety, he quickly resumed both his medical studies as a student and a research program, focusing his efforts in the study of diabetes, glucose, and insulin. In 1941, he completed his medical education and decided to pursue scientific research as a full-time career, rather than practice medicine.

During the war, he also married Janine Herman in September of 1943. It was a marriage that would last 65 years. The de Duve couple had four children, two girls, and two boys.

3) Early on, he studied insulin and its role in diabetes mellitus. First, I know that insulin kind of serves as a lock and key in terms of sugar and energy production—but can you take this one step further and help those who are afflicted with diabetes—either Type I or Type II?

Diabetes can best be described as a disorder in the amounts of glucose in the blood of the patient. Individuals who suffer from diabetes may experience too much blood glucose. The medical term, diabetes mellitus, refers to the excessive urination accompanied by the presence of excessive amounts of sugar in the urine.

Type 1 diabetes has a technical term as well, insulin-dependent diabetes mellitus (IDDM). The condition often manifests itself during the childhood of the patient. The ailment is brought about by an autoimmune reaction to the patient’s pancreas, often damaging or even destroying the organ. Thus, IDDM patients cannot biosynthesize needed insulin. Consequently, without insulin, the patient cannot control the amounts of blood glucose, and the sugar levels will rise to abnormal levels. Treatment involves periodic insulin administration for the daily life of the patient.

Type 2 diabetes is also regarded as insulin-resistant diabetes and non-insulin-dependent diabetes mellitus (NIDDM). The disease will quite frequently emerge in a patient at the adult level of life. Its onset is reported to correlate with obesity, inflammation, and infection. Treatment of NIDDM can involve the administration of specific medications, such as insulin, or perhaps the more recently developed SGLT2 inhibitors, which regulate the entry into the membranes of a patient’s cells of blood glucose via the glucose transporter SGLT2. These medications help to adjust or maintain optimal glucose concentrations.

Addressing both types 1 and 2 diabetes also involve disease management, such as diet, exercise, and monitoring of blood glucose. Diabetes continues to be a severe problem in modern times. During the 1950s, however, de Duve had become interested in how insulin underwent its glucose regulatory activity. Thus, his early studies involved his interest in discovering the mechanism by which insulin acts, its mode of action. He is also credited for contributing towards the rediscovery of the hormone glucagon. His doctoral thesis had been based on this type of work, which was published as a book called Glucose, Insulin, and Diabetes. While his work in carbohydrate metabolism was fruitful in that it formed a basis for his thesis work and it established de Duve as a bona fide biochemistry investigator, he, unfortunately, never did find the mode of insulin’s action as he had initially hoped.

Instead, he pursued what he called an “accidental finding.” De Duve’s “accident” was to ultimately lead to vastly more critical discoveries. His new serendipitously inspired work led to the Nobel, which, in 1974, he shared with Drs. George E. Palade (discussed elsewhere in this book) and Albert Claude.

4) He earned the Nobel Prize for Physiology or Medicine in 1974. First, what exactly did he do to win the Nobel Prize? How did he discover the cell organelles—Peroxisome and lysosome, which were evidently discovered by accident! Second, how did this happen?

As I eluded to above, de Duve’s work on insulin action was diverted towards an entirely different line of studies, leading to his discoveries of lysosomes and peroxisomes, and the Nobel. The putative connection between these two seemingly distinct areas of research could be bridged by an enzyme.

De Duve began this serendipitous scientific journey to the Nobel in 1949. As I mentioned above, he was interested in the mechanism of insulin action. He was testing the hypothesis that insulin somehow regulated its effects on glucose by working on an enzyme involved in carbohydrate metabolism. The protein was called glucose-6-phosphatase, which we know catalyzes the conversion of glucose-6-phosphate into free glucose plus free phosphate in the liver. Once liberated, glucose can be transported to the outside of the liver cell via dedicated glucose transporters. The aim was to purify this glucose liberating enzyme.

https://upload.wikimedia.org/wikipedia/commons/9/98/Lysosome.jpg

https://upload.wikimedia.org/wikipedia/commons/9/98/Lysosome.jpg

Figure Lysosome

In the lab, de Duve first took livers from rats and prepared liver extracts by using a high-powered centrifuge and a sort of kitchen-blender and testing the extract for enzyme activity, which they found in high levels. De Duve once described this type of work as “exploring cells with a centrifuge.”

Very quickly, however, De Duve encountered a problem.

When he tried to isolate the glucose-6-phosphatase from the liver extract, he failed to solubilize the enzyme in a buffer so he could measure its activity in pure form. This was a necessary step if he wanted to be successful in his efforts. He had to purify the enzyme and measure the enzyme activity of the isolated protein to demonstrate that he was on the right track. It would be impossible to convince his colleagues that he was successful in this enzyme isolation attempt if he could not dissolve the enzyme first.

He tried a new technique, called cellular fractionation, to overcome this solubility problem.

First, De Duve dispensed with liver extracts, which destroyed the cells into a mess. Instead, he obtained the rat livers, but this time he gently prepared liver cells, keeping them intact, at first. Next, he broke the individual liver cells into their sub-cellular parts and isolated the various sections. One of these fractionated cellular parts, called microsomes, held his previously elusive enzyme activity!

This is where the laboratory “accident” occurred that would change his direction of research, and his life. As a control, de Duve included another enzyme called acid phosphatase, to show the efficacy of the fractionation process. The accident came in the form of an unexpected failure.

While the desired enzyme, the glucose-6-phosphatase, was active, the control enzyme, on the other hand, the acid phosphatase, seemed not to work. The control enzyme was inactive when it should have been quite active. It was not. So, de Duve stored his inactive control acid phosphatase in the laboratory’s refrigerator for a few days. Upon returning to the refrigerated control enzyme five days later, de Duve, by chance, measured its activity. The control enzyme worked to high levels! But it took storing the prepped protein at cold temperatures for several days to make acid phosphatase work.

De Duve speculated that the refrigeration temperatures and time permitted the acid phosphatase to overcome the membrane barrier inherent in the microsome fraction of the cell by possibly escaping from an enclosed obstacle. This barrier took the form of a membrane-enclosed vesicle, which held the inactive acid phosphatase, and which was activated by additional enzymes, called hydrolases. These hydrolases needed the time and temperature to accomplish their task, namely, enabling the acid phosphates. These enclosed sub-cellular vesicles containing powerful hydrolytic enzymes came to be known as lysosomes because once activated, they could actively undergo their lysing action, cleaving proteins to turn them on.

The discovery of the lysosomes in 1955 proved to be the one accidental discovery that earned a Nobel for de Duve.

The peroxisomes were also discovered by the laboratory of de Duve. Similar in nature to the Nobel worthy lysosomes, the peroxisomes were purified in much the same way as had been done with the lysosomes. He called these new sub-cellular parts microbodies, and these peroxisomes were found to contain certain enzymes called oxidases that produced peroxide molecules, which could be toxic to specific membranes or other substances. The peroxisomes were shown to be important in the oxidation of fatty acids and the metabolism of amino acids. In summary, both the lysosomes and the peroxisomes, discovered by de Duve, proved to be of vital importance to the functions of the living cell.

5) He worked on the purification of penicillin—which we all know is a kind of “wonder drug” what were his contributions in this area?

De Duve’s work with penicillin purification was performed while he was a graduate student in chemistry during the mid-1940s. This work formed the basis of his master’s thesis, which he defended successfully in 1946. The M.S. degree was earned at the Cancer Institute, which was a part of the Catholic University at Leuven.

By this time, however, de Duve had already had an M.D. in hand. His order of degree-seeking had been brought about because of a shortage of laboratory supplies that were needed to study insulin. This scarcity in supplies combined with the Second World War interruption served to induce de Duve to acquire a new set of skills in a laboratory that was better equipped and the work of which could be useful, namely purification of penicillin. The pursuit of another degree, albeit in chemistry, also allowed de Duve to hone his skills in biochemistry. Thus, the study of chemistry would permit de Duve to continue his interest in biochemistry. In an interview, he related that his interest in studying biochemistry was viewed by his peers as tantamount to “kitchen chemistry.” Thus, he settled for officially pursuing a graduate degree in chemistry, which was considered more of a bona fide field of study than biochemistry. Fortunately, for us, de Duve made tremendous strides in establishing biochemistry as an acceptable academic discipline.

Once de Duve entered the graduate laboratory, he used discarded milk bottles and used them to grow cultures of penicillin-producing mold. In order to get his hands on these used milk bottles, however, he and his colleague Piet De Somer had to travel back and forth to the milk plant Soprolac, Inc. With traveling restricted because of the war, this, in turn, required that De Somer and de Duve go 38 km by the only means available, which was a 1928 Amilcar and which harvested a great deal of attention from bystanders. De Duve was to recall that they were the center of attention because of the car, which required a crankshaft to start and lacked a top and a battery! They were consequently met with a roar of laughter by witnesses as they journeyed along the way between Leuven and Genval, Belgium, in pursuit of spent milk bottles.

All humor aside, de Duve employed the then known laboratory techniques, those not held secret by patents, and managed to purify several milligrams of penicillin! The accomplishment was the first time in Belgium’s history that it acquired any sort of penicillin whatsoever. This preliminary work was judged to be just enough of proper chemistry and not necessarily kitchen chemistry to satisfy the requirements for a master’s.

6) He apparently did some work on the endosymbiotic theory- what exactly is this theory, and what was his contribution?

Evolutionary biology holds that prokaryotic and eukaryotic cells share a common ancestor, and this life process is thought to involve ancient forms of prokaryotes. The endosymbiotic theory arises out of this well-established theory regarding the origin of cellular life on Earth.

The endosymbiosis theory thus proposes that prokaryotes served to reside and take hold inside the cells of eukaryotic cells, forming new organelles living as symbionts; hence, the name endosymbiosis. Part of the theory maintains that these primordial ancestors became new organelles.

This endosymbiosis postulate was formulated by Drs. Konstantin Mereschkowski at the turn of the 20th century and Lynn Margulis in the late 1960s. They had in mind the mitochondrion, which has long been known to serve as an ATP factory in all eukaryotic cells, but which was also known to have been derived from an ancient prokaryotic infection of a primitive eukaryotic cell.

In 2007, de Duve published in Nature Reviews Genetics an influential essay in which he evaluated the current literature at the time regarding the origins of eukaryotic organisms. He assessed the scientific evidence available at the time regarding two disparate theories.

The first idea was that during evolutionary history, two ancient prokaryotes fused together, and one of these organisms became a host for the other, which then took the role of the symbiont.

The second idea was that ancient cells developed the ability to endocytose nutrients from outside in order to digest them inside the cell and then used this process to establish the organelles. De Duve felt that it was the preferred idea, and it seems to have withstood the test of time. He further postulated that eukaryotic cells transitioned from acquiring nutrients by endocytosis to acquiring prokaryotes by the same process.

Based on this premise, he made another contribution to the famous endosymbiotic theory, and it had to do with his Nobel-winning lysosomes and peroxisomes. He proposed that his peroxisomes were life’s first endosymbionts and, thus, the first to give rise to new organelles. His rationale for this postulate was that the development or acquisition of peroxisomes permitted cells to resist the toxic effects of deadly oxygen gas that pervaded primordial Earth. During this ancient time, oxygen readily oxidized biomolecules by stealing their needed electrons and destroying these important biomolecules in the process. The oxidizing neutralizing enzymes pocketed within peroxisomes prevented this cellular destruction. However, because peroxisomes do not have a genomic DNA content of their own, de Duve’s version of this theory is not widely accepted by evolutionary biologists. Even de Duve himself maintained that his postulate at the time was speculative.

7) Back in 1984—he wrote a book A Guided Tour of the Living Cell—any idea as to what this book contained and why it is valued even today?

De Duve was a productive writer, and he published on a wide variety of topics. His A Guided Tour of the Living Cell, published in a handsome two-volume set, remains an influential book to this day. The book was founded on a series of presentations he had given to high school students and later university students at Rockefeller University. In his book, he guides the reader through the various parts of a typical eukaryotic cell, giving a detailed tour of the workings associated with a live cell. Illustrator Neil Hardy provides an elegant representation of the molecular, cellular structures.

He invites the reader to imagine what it is like to shrink themselves down to the size of a tiny eukaryotic cell. Or, if one prefers, he asks the reader to imagine enlarging a living cell to the size of the reader. He then leads the reader to accompany him along with the various cellular locations, starting from its outside features. In any case, the reader became a “cytonaut,” exploring the cell from a novel perspective.

Almost immediately after publication, the book was widely acclaimed as a masterpiece. One of us (MFV) recalls learning for the first time, in the late 1980s, about de Duve and his new book, from a fellow graduate student while at a small scientific retreat in the mountains of New Mexico.

8) He worked on both sides of the Atlantic- in Stockholm at the Karolinska Institute and in St. Louis, Missouri—what were some of his endeavors in each place?

In 1946, as a postdoctoral fellow in Stockholm de Duve worked in the laboratory of Hugo Theorell, who was located at the Karolinska Nobel Medical Institute. Theorell was to become a Nobel Laureate later in 1955. Theorell had been famous for discovering the so-called oxidoreductases that were important for cellular respiration. In Thorell’s laboratory, de Duve acquired the skills necessary to become an able enzymologist. This education would prove to be invaluable when the study of the acid phosphatase and the glucose-metabolizing enzymes became indispensable.

Shortly after spending a year and a half in Stockholm, de Duve acquired a fellowship from the Rockefeller Foundation and moved to study in the laboratory of the famous scientific couple Drs. Gerty and Carl Cori at Washington University. The Coris featured in chapter 21 of our first book The Inventions and Discoveries of the World’s Most Famous Scientists, were to share a Nobel Prize in 1947 for their discovery of the very famous Cori cycle. The cycle is still vital to this day for its involvement in the metabolism of glycogen, the storage form of carbohydrates.

In the Cori lab, de Duve spent half a year in which he studied alongside future Nobel Laureate Earl Sutherland. Together de Duve and Sutherland examined the contamination products of glucagon upon the activity of insulin. These contamination factors were known then as the so-called hyperglycemic-glycogenolytic (H-G) factors. The work established or rather re-established the importance of glucagon for increasing the blood levels of glucose, an effect that was counteracted by insulin.

9) After de Duve earned the Nobel Prize in 1974, King Baudouin elevated him to the title of Viscount in 1989. Do you have any idea what a Viscount means in Belgium? 

The accolade of Viscount was granted to de Duve for having made enormous contributions to biochemistry and in advancing the progress of scientific research regarding the live cell. Attaining the rank of Viscount is considered prestigious. In Belgium, it is deemed to be tantamount to achieving one of its highest honors.

Indeed, Belgium has gone one step further. In 1974 De Duve established the International Institute of Cellular and Molecular Pathology in Brussels. In 2005, it was renamed the de Duve Institute and resided at both the Catholic University of Louvain and in Brussels. The de Duve Institute is, to this day, a prestigious institution. The faculty at the de Duve institute are diverse and study a wide range of biological themes, all having to do with the biomedical sciences.

10) Apparently, we owe a debt of gratitude to the Viscount for coining various terms and words—and very salient scientific terms. In 1955, he gave us the term lysosome, and then peroxisome (1966), autophagy, endocytosis, and exocytosis—he later seemed to joke that he “was in a word coining mood.” Briefly, can you tell us why each of these words is important in the realm of science?

Indeed, when an investigator discovers novel scientific phenomena, she or he often has the unique opportunity to coin new terms that clearly convey the new functional nature of their findings. Such occasions might come along once or twice in a scientist’s lifetime. Viscount de Duve was most certainly involved in establishing new terminology, and his remarkable array of scientific coinage is genuinely unprecedented. It has been reported that de Duve coined autophagy, endocytosis, and exocytosis in one fell swoop at a conference in 1963 while he was experiencing a “word-coining mood.”

Let us start with the lysosome, a cellular entity he is widely credited for having discovered, in 1955, as evidenced by the bestowment of the Nobel. In 2005, de Duve published a retrospective entitled The Lysosome Turns Fifty. His tribute relates to the reader that the lysosome term is Greek for “digestive body,” which is a reference to the fact that these miniature cellular components are involved in the internal digestion of media derived from extracellular locations. These organelles are covered by a membrane, and they harbor digestive enzymes, which become hydrolytically active when the internal pH of the lysosome becomes acidic.

In de Duve’s reflective treatise, he related an amusing anecdote. He affirmed that at the time of his coinage of the word lysosome, he regarded biochemists as astute enough to discern between his new term and that coined by the famous Alexander Fleming, who discovered and coined the term lysozyme. De Duve admitted that his trust in the biochemists of the day to know the difference between lysosome and lysozyme was sadly misplaced. One outcome of the confusion was that de Duve was often incorrectly given credit for Fleming’s lysozyme discovery.

The term peroxisome refers to another organelle discovered by de Duve in 1965. Like the lysosomes, the peroxisomes are enclosed by a membrane and reside inside the cytoplasm of most, if not all, eukaryotic cells. The primary difference, however, is that peroxisomes harbor enzymes, e.g., catalase, that converts hydrogen peroxide to water and oxygen. Additional proteins function by exploiting the oxygen to further oxidize organic molecules. In general, peroxisomes can differ depending on the nature of the organism or cell type in which they reside. Thus, functions mediated by the peroxisomes include fatty acid breakdown (β-oxidation), phospholipid metabolism of myelin in nerve tissue, and metabolism of sugars and alcohols. In humans with aberrant peroxisome function, plasmalogen formation may be defective, resulting in severe neurological dysfunction.

De Duve coined the term autophagy in 1963. The word refers to the destruction of the cell’s own internal garbage, such as elements of the cytoplasm or worn-out organelles. De Duve’s lysosomes accomplish this cellular clean up of its own debris. The process involves internal membranous structures called phagophores that encircle cellular debris to wrap around it to produce autophagosomes when then carry its contents to the lysosome for destruction. When de Duve observed the data, he referred to the process as self-digestion, and thus, autophagy.

Endocytosis and exocytosis represent the uptake and export of biological material into and out of a cell, respectively. Often endocytosis is used interchangeably with pinocytosis or phagocytosis but could be regarded distinctively. Pinocytosis means “cell drinking” and denotes a type of endocytosis in which materials that are water-soluble are brought into a cell. Phagocytosis also undergoes endocytosis (uptake) but involves in some cases specialized cells that destroy foreign agents, like microbial pathogens, in order to protect the body. Macrophages and neutrophils are considered prime examples of phagocytes.

https://upload.wikimedia.org/wikipedia/commons/thumb/1/1a/Endocytosis_types.svg/2000px-Endocytosis_types.svg.png

https://upload.wikimedia.org/wikipedia/commons/thumb/1/1a/Endocytosis_types.svg/2000px-Endocytosis_types.svg.png

Figure Endocytosis

Exocytosis involves the excretion of degraded cellular products after they have been destroyed by hydrolytic enzymes within lysosomes. The process consists of the fusion of internal vesicles with the inside of the plasma membrane to release the degraded substances to the outside milieu of the cell.

11) Sadly, at age 95, suffering from cancer and atrial fibrillation, he decided to end his life via legal euthanasia, leaving behind a large number of books, and immense contributions to the field. What do you think are his main contributions or his legacy?

In a word, de Duve’s contributions to science are legion. His written body of scientific and popular literature is immense. In modern times, his works remain influential in science, philosophy, and history. Many of his discoveries are regularly treated in current textbooks of biology, biochemistry, and cell biology. Readers of his popular literature are enthralled by his elegant writings about the nature of the cell.

As a human being, he was amicably regarded by colleagues and students alike. After his death from cancer on the fourth day of May, in 2013, many endearing tributes emerged from those who knew him well and who felt themselves fortunate to have known him. In 2012, de Duve was featured in a documentary, emphasizing his passion for the love of science. Hence, if I may be so bold, I believe that this will ultimately be his enduring legacy: affording a compelling enthusiasm for learning, especially about the internal workings of a living cell.

For further information about this remarkable scientist, visit:

Stories by Christian de Duve: https://www.scientificamerican.com/author/christian-de-duve/

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