Aaron Ciechanover

Aaron Ciechanover was born in Haifa on October 1, 1947, before the establishment of Israel.[1] His parents were Jewish immigrants from Ciechanów, Poland, who had moved to Palestine in the mid-1920s; the family surname derives from their city of origin.[3] His father, Isaac, also identified as Yitzhak, was a lawyer, while his mother, Bluma, worked as a clerk and English teacher.[1][3] Both parents placed a strong value on education, an influence that Ciechanover later emphasized when discussing the origins of his scientific career.[4]

Orphaned while young, Ciechanover grew up in his aunt's home.[5] His older brother Yossi became an important parental figure and remained closely involved in his life.[5] In later reflections on his upbringing, Ciechanover credited not only his family but also his teachers with giving him a love of learning, language, and logical thought.[4] He attended Hugim high school in Haifa, where chemistry teacher Naama Greenspan helped shape his direction.[4] Looking back on his education, he regarded himself as a product of Israel's early educational system and singled out Greenspan's influence on his career.[4]

After graduating from high school in 1965, Ciechanover began medical studies at Hadassah.[1] He studied at the Hebrew University–Hadassah Medical School in Jerusalem through the Israel Defense Forces' academic reserve program.[4] He later recalled that his mother had encouraged him to become a physician, but that clinical medicine ultimately did not provide the career he wanted.[6] During his residency, he decided to move away from medical practice and pursue doctoral research.[6] His medical training nevertheless preceded both his military service as a physician and his eventual work on the cellular mechanisms underlying health and disease.[7]

Ciechanover received his M.D. from the Hebrew University–Hadassah Medical School in 1974.[8] His service in the IDF Medical Corps included work as a combat physician aboard a navy cruiser and later in the Research and Development Unit at the Chief Medical Officer Headquarters.[1] He served as a naval physician during the Yom Kippur War.[4] Recalling the sequence of his training, he described completing his medical degree, performing military service, and then pursuing a doctorate; he characterized the medical and doctoral courses as seven and five years of study, respectively.[7]

At the Technion's Faculty of Medicine in Haifa, Ciechanover pursued graduate research under Avram Hershko, studying biochemistry and the breakdown of proteins.[5][8] He began doctoral work with Hershko in 1976, and the two spent five years investigating the mechanism responsible for protein degradation inside cells.[5] Choosing this project meant accepting considerable uncertainty: Hershko warned him that the proposed work was risky because the existence of the protein-destruction system they hoped to investigate was not assured.[7] Ciechanover later recalled that this uncertainty attracted rather than discouraged him, and that he welcomed the risk involved in the research.[7]

The collaboration extended beyond Haifa to the Fox Chase Cancer Center in Philadelphia, where Ciechanover, Hershko, and American researcher Irwin Rose worked together on protein degradation in the late 1970s and early 1980s.[9] Ciechanover and Hershko also carried out their investigations at the Technion, with support from the Israel Cancer Research Fund.[10] Their work established that the removal of unwanted proteins is a regulated cellular process in which selected proteins are marked for destruction, rather than a matter of indiscriminate breakdown.[2]

The central component of this process is ubiquitin, which attaches to proteins that are damaged or no longer needed.[2] The attached ubiquitin acts as a signal directing the selected protein toward a proteasome, a structure containing enzymes that break proteins into amino acids.[2] Before the targeted protein enters the proteasome, the ubiquitin detaches and becomes available for reuse.[2] The resulting protein components can also be reused to make functional proteins, linking the disposal of unwanted material to the production of new cellular material.[7]

Ciechanover explained the importance of this turnover by distinguishing two reasons why a cell must destroy proteins.[11] First, proteins can become defective when their structures are damaged, including through genetic changes, temperature, radiation, or environmental pollutants.[11] Second, even an undamaged protein may need to be removed once its task has been completed, so that it does not continue acting at an inappropriate time.[11] The ubiquitin system supplies selectivity by tagging proteins designated for destruction while leaving unmarked proteins intact.[11] In this account, protein breakdown is both a means of clearing defective material and a mechanism for controlling the timing of biological activity.[11]

In explaining the scale of protein turnover, Ciechanover estimated that about 5 percent of the body's proteins are replaced each day, while some are replaced within minutes.[7] He described more than a thousand enzymes as participating in the identification of proteins for ubiquitin tagging, with the proteasome carrying out their destruction.[7] As an example of the need for timely removal, he pointed to proteins involved in cell division: once division is complete, those proteins must be destroyed, because retaining them could allow them to act again and contribute to uncontrolled division.[7] The system thus serves as part of the body's protein quality control while also regulating proteins that have already fulfilled their functions.[7]

The researchers showed that ubiquitin-mediated degradation helps regulate cell division, the repair of DNA defects, and gene transcription.[2] Other processes associated with the system include differentiation, signal transduction, intracellular trafficking, and quality control.[12] Parts of the immune response are also affected by the ubiquitin system.[13] These functions extend its significance beyond the removal of damaged proteins: the same general mechanism participates in regulating when proteins act and when their activity must end.[2][11]

Ciechanover received his doctorate from the Technion in 1981 and undertook postdoctoral research at the Massachusetts Institute of Technology.[1][3] His postdoctoral period lasted from 1981 to 1984 and included research on receptors, including transferrin receptors.[3] At MIT, he and Alexander Varshavsky identified the first mutant cell in the ubiquitin system.[5] This work followed his investigations with Hershko and Rose and preceded his return to Israel, where he established his own laboratory.[1][5]

Returning to Haifa in 1984, Ciechanover established a research laboratory in the biochemistry department of the Technion's Faculty of Medicine.[1] He began independent work in the Technion's Unit of Biochemistry in 1986.[8] His academic career included research and teaching at the Technion.[4][8] He held the Janet and David Polak Chair in Life Sciences and directed the Rappaport Family Institute for Research in the Medical Sciences during the 1990s, continuing as director until 2000.[12] Alongside his own investigations, he trained graduate students and helped shape a generation of Israeli scientific and medical researchers.[1]

Recognition of his research accumulated before the Nobel award.[12] He received the Henry Taub Prize for Excellence in Research in 1997 and shared the Wachter Prize with Hershko in 1999.[12][3] In 2000, Ciechanover and Hershko received the Albert and Mary Lasker Award for Basic Medical Research together with Alexander Varshavsky.[5] The EMET Prize followed in 2002, and Ciechanover received the Israel Prize in biology in 2003.[12] The Israel Prize committee emphasized the far-reaching implications of his research for understanding the molecular basis of diseases, particularly cancer.[5]

In 2004, Ciechanover shared the Nobel Prize in Chemistry with Hershko and Rose for the discovery of ubiquitin-mediated protein degradation.[2] Ciechanover and Hershko were the first Israeli scientists to win a Nobel Prize in science.[2] Ciechanover was also the first of four Nobel laureates to graduate from the Technion.[14] The award recognized a collaboration that connected research in Haifa and Philadelphia and explained how cells selectively remove unwanted proteins.[2][9]

After receiving the Nobel Prize, Ciechanover continued working in his laboratory at the Technion's Faculty of Medicine.[7] He described the award as leaving his central activity unchanged: he still enjoyed science and laboratory work, just as he had during the preceding decades.[7] His description of research as a hobby for which the Technion paid him conveyed the personal enjoyment he took in scientific work.[7] A 2011 profile described him as continuing research related to cancer medicines at the Technion, and a 2019 account identified him as a research professor at the Rappaport Institute.[4][15]

His later scientific activities also included work outside Israel.[14] In 2018, he opened the Ciechanover Institute of Precision and Regenerative Medicine in Shenzhen, China.[14] In 2019, he joined the advisory committee to the board of Panaxia, a medical-cannabis company.[15] He explained his decision as grounded in a scientific rather than mystical approach, citing discussions with the company and the involvement of fellow Technion researcher David Meiri as influences on his choice.[15]

Ciechanover also participated in public discussions extending beyond laboratory research.[16] On June 12, 2018, he joined Rabbi Sacks at the Technion in Haifa for a conversation titled “Does God Play Dice? A Dialogue on Science and Religion.”[16] During that exchange, Ciechanover argued that science was defined by the testing of hypotheses rather than by religious commitments: “Science is not religious. Science is a system of testable hypotheses that you should go to the laboratory, to the computer, to see whether the hypothesis is correct or wrong.”[16]

In a separate 2018 address to Jewish diplomats, Ciechanover described himself as a typical Israeli and emphasized the human benefit of his scientific work.[6] He said that his greatest sense of accomplishment came from knowing that his discovery helped heal people and save lives.[6] In the same address, he cited figures of 0.2 percent for Jews' share of the world population and 27 percent for their share of Nobel Prizes, presenting them as part of his discussion of Jewish achievement.[6]

The discovery of ubiquitin-mediated protein degradation connected a fundamental cellular mechanism with the understanding of disease.[2] When the system does not function normally, the consequences can include illnesses such as cystic fibrosis.[2] Accounts of its medical significance also identify cervical cancer, while disruptions of protein-removal processes have been associated with malignancies and neurodegenerative diseases.[17][11] The research provided a basis for investigating how failures of protein handling contribute to illness and for developing medicines directed at those processes.[2][11]

One documented therapeutic application is Velcade, used to treat multiple myeloma, a cancer of plasma cells.[9] The ubiquitin discovery was foundational to the development of this treatment.[9] Velcade works by inhibiting the protein-degradation system in a way that can be used against cancer cells.[5][9] Ciechanover compared the effect to a sanitation strike, using the accumulation of material awaiting disposal to explain how blocking cellular waste removal could become a therapeutic strategy.[10] This application illustrates a medical consequence of understanding the machinery of protein destruction rather than simply identifying an association between a protein and a disease.[10][9]

The treatment connection also reflected the breadth of the original finding: ubiquitin-mediated degradation is involved in ordinary cellular maintenance as well as in the regulation of processes that can become abnormal in disease.[2][12] The system removes damaged proteins, disposes of proteins whose work is complete, and participates in controlling cell division and other activities.[7] Understanding its selectivity therefore contributed both to knowledge of normal cell function and to research on what happens when that regulation fails.[2][11] Ciechanover's medical training and subsequent laboratory career brought him from treating patients directly to investigating a mechanism with implications for treatment.[1][7]

Public explanations of the discovery were another part of his activity.[7][18] Speaking with a young interviewer in his Technion laboratory, he used a molecular model and called the mechanism “the garbage machine of the body,” describing how it removes damaged proteins and makes room for new ones.[18] In other interviews, he explained the reuse of protein components and the need to eliminate proteins after a particular task was complete.[7] These explanations presented protein destruction not as mere loss, but as a selective process necessary for cellular maintenance and renewal.[7][18]

Ciechanover's contribution to Israeli science included the laboratory and training environment he established after returning from the United States.[1] At the Technion, he trained graduate students and influenced a generation of Israeli researchers in science and medicine.[1] His work with Hershko made Haifa one of the locations associated with the Nobel-recognized discovery, while their joint award marked the first Nobel recognition of Israelis in science.[2][9] His later establishment of an institute in Shenzhen added an international institutional dimension to a career rooted in the Technion.[14]

His professional recognition extended to membership in leading scientific academies.[1] He was a member of the Israel Academy of Sciences and Humanities and the Pontifical Academy of Sciences, and a foreign associate of the United States National Academy of Sciences.[1] These memberships accompanied honors spanning basic medical research, Israeli biological research, and chemistry, including the Lasker Award, Israel Prize, and Nobel Prize.[2][12] Across his reflections on these achievements, he continued to emphasize the pleasure of doing science and the satisfaction of knowing that his work could help patients.[7][6]

Ciechanover became a vocal participant in protests against the Israeli government's judicial reform initiative.[19] At a 2024 National Emergency Conference in Kibbutz Nir Oz, he linked the departure of Israeli professionals to political conditions and warned about the country's ability to retain people essential to its future.[19] He argued that the loss of a relatively small group could have severe national consequences, saying, “as soon as 30,000 of these people leave, we won't have a country here.”[19] The statement expressed his political assessment of the danger of professional emigration, rather than an established demographic threshold.[19]