Mini Museum 3: Rodbell and the G-Coupled Protein by Ian Fairfield

Early Theories of Cell Communication

ianfairf31 — 2025-02-21 15:56:40 UTC

In 1855, Claude Bernard, a French physiologist, introduced the concept of “internal secretions,” revolutionizing the understanding of how cells communicate within the body (Gross, 1998). Bernard’s research demonstrated that certain organs release substances directly into the bloodstream, allowing for the regulation of physiological processes at distant sites, a foundational concept that paved the way for future discoveries in cell signaling and endocrine regulation (Nair et al., 2019).

Bernard’s work was groundbreaking because it challenged the prevailing notion that bodily functions were solely controlled by the nervous system. Instead, he proposed that the internal environment of the body must remain stable despite external changes, an idea now recognized as homeostasis (Gross, 1998). This principle established a new way of thinking about physiological regulation, highlighting the role of chemical messengers in maintaining balance within the body.

His research directly influenced later studies on hormonal regulation, neurotransmitter function, and molecular signaling, all of which became integral to understanding how cells communicate and regulate bodily functions (Nair et al., 2019). The idea of internal secretions laid the groundwork for the discovery of hormones and neurotransmitters, which became essential in understanding neurological function and intracellular signaling pathways (Gross, 1998).

Bernard’s contributions remain a cornerstone of modern physiology, endocrinology, and neuroscience, shaping the study of cell signaling mechanisms and influencing the later discovery of G-proteins, the focus of Martin Rodbell’s Nobel Prize-winning research (Nair et al., 2019). His pioneering ideas on the body’s internal regulatory mechanisms continue to be studied today, serving as a crucial link between early physiological theories and modern molecular biology.

Sources:

Gross, C. G. (1998). Claude Bernard and the constancy of the internal environment. The Neuroscientist, 4(5), 380–385. https://doi.org/10.1177/107385849800400520

Nair, A., Chauhan, P., Saha, B., & Kubatzky, K. F. (2019). Conceptual evolution of cell signaling. International Journal of Molecular Sciences, 20(13), 3292. https://doi.org/10.3390/ijms20133292

Discovery of Hormones

ianfairf31 — 2025-02-21 19:05:47 UTC

In 1905, Ernest Starling, a British physiologist, introduced the term “hormone” to describe chemical messengers released into the bloodstream to regulate distant organs (Henderson, 2005). His groundbreaking work on secretin, a substance produced by the small intestine that stimulates pancreatic secretion, provided the first direct evidence of chemical signaling in physiology. This discovery challenged the prevailing belief that only the nervous system controlled bodily functions and established the endocrine system as a distinct regulatory network (Henderson, 2005).

Starling’s research built upon earlier work by physiologists like Claude Bernard, who had introduced the concept of internal secretions, and William Bayliss, with whom Starling co-discovered secretin (Henderson, 2005). Their experiments demonstrated that the digestive system could communicate with distant organs without neural input, fundamentally shifting scientific perspectives on physiological regulation.

The identification of hormones as chemical regulators of bodily processes laid the groundwork for future discoveries in cell signaling, neurotransmission, and receptor biology. Starling’s findings influenced later research into hormone-receptor interactions, intracellular signaling pathways, and the role of second messengers like cyclic AMP, which became essential in understanding G-protein signaling, the focus of Martin Rodbell’s Nobel Prize-winning research (Henderson, 2005).

Today, the field of endocrinology and molecular signaling continues to build upon Starling’s contributions. His introduction of the term hormone marked a turning point in biomedical science, leading to a more comprehensive understanding of how cells communicate and regulate physiological processes.

Source:

Henderson, J. (2005). Ernest Starling and ‘Hormones’: an historical commentary. Journal of Endocrinology, 184(1), 5–10. https://doi.org/10.1677/joe.1.06000

Receptors in Physiology: Foundation for Signal Transduction

ianfairf31 — 2025-02-21 19:10:01 UTC

In the early 1900s, Paul Ehrlich, a German physician and scientist, introduced the concept of cell receptors, fundamentally changing our understanding of how cells interact with their environment (Strebhardt & Ullrich, 2008). His research proposed that cells possess specific receptors that bind to toxins and antitoxins, a revolutionary idea that later extended beyond immunology into hormonal signaling and neurotransmission.

Ehrlich’s receptor theory laid the groundwork for the modern understanding of signal transduction, suggesting that only molecules with the correct structural fit could trigger cellular responses (Strebhardt & Ullrich, 2008). This “lock and key” mechanism became a central concept in biochemistry and pharmacology, influencing studies on hormones, neurotransmitters, and intracellular signaling pathways.

By establishing that cells use specialized molecular structures to detect and respond to external signals, Ehrlich’s work provided a critical foundation for later discoveries in G-protein-coupled receptor (GPCR) research. His ideas directly influenced later studies on membrane receptors and intracellular messengers, ultimately leading to the recognition of G-proteins as key mediators of cellular communication.

Today, Ehrlich’s receptor theory remains one of the most important principles in molecular biology and neuroscience, influencing drug development and our understanding of how cells process information from their environment. His pioneering work continues to impact research on cell signaling, receptor activation, and intracellular pathways, key components of modern neuroscience and biomedical science.

Source:

Strebhardt, K., & Ullrich, A. (2008b). Paul Ehrlich’s magic bullet concept: 100 years of progress. Nature Reviews. Cancer, 8(6), 473–480. https://doi.org/10.1038/nrc2394

Discovery of Neurotransmitter: Otto Loewi's Work in the 1920s

ianfairf31 — 2025-02-21 19:10:53 UTC

In 1921, Otto Loewi, an Austrian pharmacologist, provided the first direct evidence of chemical transmission in neural communication, revolutionizing neuroscience and the study of cell signaling (Bennett, 2000). His groundbreaking experiment, often called the "dream experiment," demonstrated that nerve impulses could be transmitted via chemical messengers rather than purely electrical signals.

Loewi’s experiment involved stimulating the vagus nerve of a frog’s heart, which caused the heart rate to slow. He then transferred the fluid surrounding the heart to another frog’s heart, observing the same slowing effect, thereby proving that the signal was chemical in nature. This neurotransmitter, later identified as acetylcholine, became the first confirmed chemical messenger in neural communication (Bennett, 2000).

Loewi’s discovery was monumental for the understanding of synaptic transmission, directly influencing research on receptors and intracellular signaling mechanisms. His work solidified the idea that cells communicate through chemical messengers, an essential concept in later studies on hormonal signaling, receptor interactions, and intracellular pathways.

The discovery of neurotransmitters like acetylcholine played a pivotal role in understanding how cells process and respond to external signals, paving the way for later breakthroughs in membrane receptor function and second messenger systems, including G-proteins. This research formed a critical link between early chemical signaling theories and the discoveries that would later lead to Martin Rodbell’s identification of G-protein signaling pathways.

Today, Loewi’s work remains foundational in neuroscience, neuropharmacology, and cellular communication, influencing treatments for neurological disorders and expanding our knowledge of how cells transmit and receive chemical information.

Source:

Bennett, M. R. (2000). The concept of transmitter receptors: 100 years on. Neuropharmacology, 39(5), 523–546. https://doi.org/10.1016/S0028-3908(99)00258-6

Mid-20th Century: Adenylate Cyclase and cAMP

ianfairf31 — 2025-02-21 19:12:25 UTC

In the late 1950s and early 1960s, Earl Sutherland, an American pharmacologist, made a groundbreaking discovery that transformed the understanding of cell signaling. He identified cyclic adenosine monophosphate (cAMP) as a second messenger, a molecule that transmits signals from hormones and other extracellular stimuli into the cell, triggering intracellular changes (Sutherland & Rall, 1958).

Sutherland’s work focused on how hormones like epinephrine influenced metabolism. He demonstrated that rather than acting directly on enzymes, hormones activated receptors on the cell membrane, which then stimulated the production of cAMP via the enzyme adenylate cyclase (Sutherland & Rall, 1958). This discovery revealed a crucial intracellular signaling mechanism that explained how external chemical signals could elicit complex physiological responses inside cells.

The identification of cAMP as a second messenger was a pivotal moment in signal transduction research, influencing later discoveries on cellular communication, receptor function, and intracellular signaling cascades. His findings laid the foundation for understanding G-protein signaling, as later research would show that G-proteins regulate adenylate cyclase activity, controlling cAMP levels within cells.

Sutherland’s discovery directly influenced Martin Rodbell’s later work on G-proteins, which explained the mechanism by which signals from hormones and neurotransmitters are transmitted through membrane-bound receptors to activate intracellular pathways. Today, cAMP remains a central concept in molecular and cellular biology, with implications for hormonal regulation, metabolism, neuroscience, and pharmacology.

Source:

Sutherland, E. W., & Rall, T. (1958). FRACTIONATION AND CHARACTERIZATION OF a CYCLIC ADENINE RIBONUCLEOTIDE FORMED BY TISSUE PARTICLES. Journal of Biological Chemistry, 232(2), 1077–1091. https://doi.org/10.1016/s0021-9258(19)77423-7

Molecular Biology Techniques: Protein Purification and More

ianfairf31 — 2025-02-21 19:15:07 UTC

In the mid-20th century, significant advancements in molecular biology techniques revolutionized the study of cellular components, particularly proteins involved in cell signaling. The development of methods such as protein purification, crystallization, and recombinant DNA technology enabled scientists to isolate and analyze proteins with unprecedented precision (Rhoads, 2024).

During the 1950s and 1960s, researchers faced challenges in obtaining sufficient quantities of pure proteins for structural studies. The introduction of protein crystallization techniques allowed for the detailed examination of protein structures, providing insights into their functions and interactions. However, the limited availability of proteins hindered progress. This obstacle was overcome in the early 1970s with the advent of recombinant DNA technology, pioneered by scientists such as Paul Berg, Herbert Boyer, and Stanley Cohen. This innovation enabled the cloning and expression of specific proteins in host organisms, producing ample quantities for research purposes. Consequently, the combination of protein crystallization and recombinant DNA technology facilitated the determination of numerous protein structures, enhancing our understanding of their roles in cellular processes (Su et al., 2015).

These technological advancements were instrumental in the discovery and characterization of G-proteins. The ability to purify and study proteins involved in cell signaling allowed researchers to elucidate the mechanisms by which cells respond to external stimuli. In particular, the identification and analysis of G-proteins shed light on their crucial role as molecular switches in transmitting signals from cell surface receptors to intracellular effectors. This understanding has had profound implications for neuroscience, pharmacology, and medicine, influencing the development of targeted therapies for various diseases (Rhoads, 2024).

In summary, the advancements in molecular biology techniques from the 1950s to the 1970s, including protein purification, crystallization, and recombinant DNA technology, were pivotal in advancing our comprehension of cell signaling pathways. These developments laid the groundwork for significant discoveries, such as the elucidation of G-protein functions, which continue to impact scientific research and medical practice today (Su et al., 2015).

Sources:

Rhoads, D. (2024, July 22). History of Cell Biology: Timeline of important discoveries. Bitesize Bio.

Su, X. D., Zhang, H., Terwilliger, T. C., Liljas, A., Xiao, J., & Dong, Y. (2015). Protein Crystallography from the Perspective of Technology Developments. Crystallography Reviews, 21(1-2), 122–153. https://doi.org/10.1080/0889311X.2014.973868

Rodbell’s Early Research: Hormones and Signal Transduction

ianfairf31 — 2025-02-21 19:15:54 UTC

In the 1960s and 1970s, Martin Rodbell, an American biochemist, conducted groundbreaking research on hormone action and signal transduction at the National Institutes of Health (NIH). His work focused on understanding how cells respond to external signals, specifically how hormones interact with receptors on the cell membrane to trigger intracellular changes (Nobel Prize). Through a series of meticulous experiments, Rodbell challenged the prevailing one-step hormone-receptor activation model, instead proposing a more complex mechanism involving an intermediate transducer molecule that relayed signals within the cell (History of Medicine).

Rodbell’s experiments revealed that hormones did not act directly on cellular processes but instead required an intermediary component to transmit signals inside the cell. His research built upon earlier discoveries, including Earl Sutherland’s identification of cyclic AMP (cAMP) as a second messenger, but sought to uncover how external signals influenced intracellular signaling pathways (Nobel Prize). His findings led him to hypothesize the existence of guanine nucleotide-binding proteins (G-proteins), a discovery that would later earn him the 1994 Nobel Prize in Physiology or Medicine.

His studies at the NIH were instrumental in shifting the scientific understanding of cell signaling and hormone action. By proposing that signal transduction involved a multistep process with distinct molecular players, Rodbell laid the groundwork for the identification of G-proteins, which play a fundamental role in neurotransmission, metabolism, and cellular communication (History of Medicine).

Today, Rodbell’s early research is recognized as a milestone in molecular biology and endocrinology, influencing advancements in pharmacology, neuroscience, and disease treatment. His findings not only explained how hormones regulate cellular functions but also opened new avenues for understanding and targeting signal transduction pathways in medicine.

Source:

Office of NIH History and Stetten Museum. (n.d.). Rodbell new model. National Institutes of Health. Retrieved from https://history.nih.gov/display/history/Rodbell+New+Model

Nobel Prize in Physiology or Medicine 1994. (n.d.). NobelPrize.org. https://www.nobelprize.org/prizes/medicine/1994/rodbell/facts/

Discovery of G-Proteins: The Breakthrough

ianfairf31 — 2025-02-21 19:19:11 UTC

In 1971, Martin Rodbell made a groundbreaking discovery that transformed the understanding of cellular communication—he identified G-proteins as essential intermediaries in signal transduction (Birnbaumer, 2007). His research demonstrated that cells do not directly respond to external stimuli through receptors alone, but instead rely on an intermediary molecular switch that transmits signals from receptors to intracellular effectors, regulating numerous physiological processes.

Rodbell’s experiments challenged the prevailing belief that hormones acted directly on target enzymes, instead proposing a three-component model of signal transduction. His findings revealed that receptors, G-proteins, and effector enzymes work together in a sequence, with G-proteins acting as signal transducers by binding to guanine nucleotides (GTP and GDP) (Birnbaumer, 2007). This insight fundamentally changed how scientists viewed cellular signaling pathways, laying the foundation for future studies on hormonal regulation, neurotransmission, and metabolism.

Unlike previous theories that described a linear interaction between hormones and enzymes, Rodbell’s discovery introduced a dynamic regulatory mechanism—G-proteins were shown to be versatile molecular switches, toggling between active and inactive states in response to receptor activation. This mechanism was crucial in explaining how cells fine-tune their responses to external stimuli, influencing research in neuroscience, endocrinology, and pharmacology.

The identification of G-proteins as signal mediators was one of the most important breakthroughs in molecular biology and medicine, directly influencing later research on G-protein-coupled receptors (GPCRs), which regulate key processes such as neurotransmitter release, sensory perception, and immune responses. Rodbell’s pioneering work ultimately led to his 1994 Nobel Prize in Physiology or Medicine, shared with Alfred G. Gilman, who further characterized the molecular structure and function of G-protein subunits.

Today, G-protein signaling remains a central focus in biomedical research, with direct applications in drug development and disease treatment, particularly in targeting neurological and metabolic disorders.

Source:

Birnbaumer L. (2007). The discovery of signal transduction by G proteins: a personal account and an overview of the initial findings and contributions that led to our present understanding. Biochimica et biophysica acta, 1768(4), 756–771. https://doi.org/10.1016/j.bbamem.2006.09.027

Expansion of G-Protein Research: 1970s–1980s

ianfairf31 — 2025-02-21 19:23:14 UTC

During the late 1970s and early 1980s, researchers such as Alfred G. Gilman and Martin Rodbell made groundbreaking discoveries that significantly advanced our understanding of G-proteins and their role in signal transduction. Their work revealed that G-proteins function as heterotrimeric complexes, composed of three distinct subunits—α, β, and γ—which play crucial roles in relaying extracellular signals from cell surface receptors to intracellular pathways (Liu et al., 2024).

One of the most significant findings during this period was the realization that G-proteins act as molecular switches by cycling between active (GTP-bound) and inactive (GDP-bound) states. This process was critical in explaining how cells regulate responses to hormones, neurotransmitters, and sensory stimuli (Milligan & Kostenis, 2006). The identification of distinct G-protein subtypes, each linked to different receptors and signaling pathways, helped unravel the complexity of intracellular communication, influencing research in neuroscience, cardiovascular biology, and pharmacology.

Additionally, these discoveries established the mechanisms by which G-proteins interact with G-protein-coupled receptors (GPCRs), a vast class of membrane receptors that regulate numerous physiological processes (Liu et al., 2024). The understanding of how GPCRs activate G-proteins laid the foundation for drug discovery and therapeutic interventions, as nearly 40% of all modern pharmaceuticals target GPCR-mediated pathways (Milligan & Kostenis, 2006).

The identification of the heterotrimeric structure and function of G-proteins was a pivotal moment in molecular and cellular biology, expanding upon Rodbell’s initial discovery and leading to a deeper comprehension of cellular signaling networks. These advancements ultimately contributed to Gilman and Rodbell being awarded the 1994 Nobel Prize in Physiology or Medicine, recognizing their profound contributions to cell signaling research.

Sources:

Liu, S., Anderson, P. J., Rajagopal, S., Lefkowitz, R. J., & Rockman, H. A. (2024). G Protein-Coupled Receptors: A century of research and Discovery. Circulation Research, 135(1), 174–197. https://doi.org/10.1161/circresaha.124.323067

Milligan, G., & Kostenis, E. (2006). Heterotrimeric G-proteins: a short history. British journal of pharmacology, 147 Suppl 1(Suppl 1), S46–S55. https://doi.org/10.1038/sj.bjp.0706405

Discovery of G-Proteins in Neurological Disorders: 1990s–Present

ianfairf31 — 2025-02-21 19:24:35 UTC

Since the 1990s, research on G-protein-coupled receptors (GPCRs) has significantly advanced the understanding of neurological and psychiatric disorders, including Parkinson’s disease, Alzheimer’s disease, and schizophrenia. As key regulators of neurotransmission and neuronal communication, GPCRs play a central role in how brain cells receive and process signals, making them crucial targets for pharmacological interventions (Catapano & Manji, 2007).

One of the most critical applications of GPCR research has been in neurodegenerative diseases, where dysregulated G-protein signaling has been implicated in dopaminergic and cholinergic dysfunction. In Parkinson’s disease, the progressive loss of dopaminergic neurons disrupts GPCR-mediated pathways, particularly dopamine receptor signaling, leading to motor impairment. Treatments such as dopamine agonists target these pathways to improve motor function and manage symptoms (Wong et al., 2023). Similarly, in Alzheimer’s disease, GPCR dysregulation is linked to amyloid-beta toxicity and neuroinflammation, influencing disease progression and cognitive decline. Targeting muscarinic and adrenergic receptors has been explored as a potential therapeutic approach (Wong et al., 2023).

GPCRs are also central to psychiatric disorders such as schizophrenia, depression, and bipolar disorder, where imbalances in serotonin, dopamine, and glutamate signaling contribute to symptoms. Many antipsychotic and antidepressant medications function by modulating GPCR activity, such as serotonin 5-HT receptors and dopamine D2 receptors, to restore chemical balance in the brain (Catapano & Manji, 2007). The continued study of GPCRs has led to the development of more targeted and effective treatments with fewer side effects.

The role of G-proteins in neurological disorders highlights the profound impact of Martin Rodbell’s discovery of G-protein signaling on modern medicine. Understanding how GPCRs regulate brain function has paved the way for innovative drug therapies that improve the lives of millions affected by neurodegenerative and psychiatric disorders. Research in this field continues to evolve, with recent advances exploring biased agonism and allosteric modulators to develop more selective and precise treatments for brain disorders.

Sources:

Catapano, L. A., & Manji, H. K. (2007). G protein-coupled receptors in major psychiatric disorders. Biochimica et biophysica acta, 1768(4), 976–993. https://doi.org/10.1016/j.bbamem.2006.09.025

Wong, TS., Li, G., Li, S. et al. G protein-coupled receptors in neurodegenerative diseases and psychiatric disorders. Sig Transduct Target Ther 8, 177 (2023). https://doi.org/10.1038/s41392-023-01427-2

G-Protein-Coupled Receptors: Modern Drug Discovery

ianfairf31 — 2025-02-21 20:21:57 UTC

Between 2010 and 2020, significant advancements in G-protein-coupled receptor (GPCR) structural biology transformed modern neuroscience and pharmacology. GPCRs, which regulate numerous physiological and neurological functions, were historically difficult to study due to their complex membrane-bound structures. However, during this period, breakthroughs in X-ray crystallography and cryo-electron microscopy (cryo-EM) enabled researchers to determine high-resolution structures of GPCRs, allowing for a more precise understanding of their function (Liu et al., 2024).

These structural insights revolutionized drug discovery, shifting the approach from random ligand screening to structure-based drug design. By visualizing how GPCRs interact with hormones, neurotransmitters, and pharmaceutical compounds, scientists were able to develop drugs with greater selectivity, reducing off-target effects and improving therapeutic efficacy (Wong et al., 2023). This knowledge was particularly impactful in treating neurological and psychiatric disorders, where GPCRs play a central role in neurotransmitter signaling.

One major breakthrough during this time was the development of biased agonists, molecules designed to selectively activate specific GPCR pathways while minimizing adverse effects. This discovery provided a new generation of therapeutic agents for disorders such as schizophrenia, depression, and Parkinson’s disease, where traditional treatments often resulted in significant side effects (Wong et al., 2023). Additionally, GPCR-targeted drugs have been increasingly explored for treating Alzheimer’s disease, given the role of GPCR dysregulation in cognitive decline.

The advancements in GPCR structural biology and pharmacology between 2010 and 2020 highlight the lasting impact of Martin Rodbell’s discovery of G-proteins. By identifying G-proteins as key mediators of cellular signaling, Rodbell laid the groundwork for understanding GPCR activation and drug targeting, shaping modern neuroscience and biomedical research.

Sources:

Liu, S., Anderson, P. J., Rajagopal, S., Lefkowitz, R. J., & Rockman, H. A. (2024). G Protein-Coupled Receptors: A century of research and discovery. Circulation Research, 135(1), 174–197. https://doi.org/10.1161/CIRCRESAHA.124.323067

Wong, T. S., Li, G., Li, S., et al. (2023). G protein-coupled receptors in neurodegenerative diseases and psychiatric disorders. Signal Transduction and Targeted Therapy, 8, 177. https://doi.org/10.1038/s41392-023-01427-2

Martin Rodbell: Pioneer of Cellular Signal Transduction

ianfairf31 — 2025-02-21 20:26:58 UTC

Martin Rodbell was born on December 1, 1925, in Baltimore, Maryland, and passed away on December 7, 1998, in Chapel Hill, North Carolina. His early life, shaped by his family's hardworking background, instilled in him a strong sense of curiosity and discipline. He attended Johns Hopkins University, where he initially pursued interests in both biology and French existential literature. However, his academic journey was interrupted in 1944 when he served as a U.S. Navy radio operator during World War II. This experience exposed him to different cultures and perspectives, deepening his interest in scientific exploration. After the war, he returned to Johns Hopkins University, completing his B.S. in biology in 1949 (NobelPrize.org).

Rodbell pursued his Ph.D. in biochemistry at the University of Washington, Seattle, which he completed in 1954. In 1950, he married Barbara Charlotte Ledermann, a Holocaust survivor and a former friend of Anne Frank’s sister, Margot. Together, they had four children (Wikipedia). Rodbell's career took off when he joined the National Institutes of Health (NIH) in Bethesda, Maryland, where he made his most significant scientific contributions (History of Medicine).

His research at the NIH led to the discovery of signal transduction mechanisms, which laid the foundation for the identification of G-proteins. He proposed a three-component model of cell signaling, showing that receptors, G-proteins, and effector enzymes work together to relay messages within the cell. This discovery redefined the field of molecular biology and significantly influenced research in endocrinology, neuroscience, and pharmacology (NobelPrize.org).

He was awarded the Nobel Prize in Physiology or Medicine in 1994, alongside Alfred G. Gilman, for their contributions to understanding G-proteins and cellular signaling. His findings remain fundamental to modern biomedical science, shaping drug development, disease treatment, and neurological research. Rodbell’s work continues to impact neuroscience and pharmacology, as G-protein-coupled receptors (GPCRs) are now the targets of nearly 40% of modern pharmaceuticals (History of Medicine).

Today, Martin Rodbell is remembered as one of the most influential biochemists of the 20th century, whose work bridged the gap between molecular biology and medicine, unlocking new ways to understand how cells communicate and respond to their environment.

Sources:

Nobel Prize in Physiology or Medicine 1994. (n.d.-b). NobelPrize.org. https://www.nobelprize.org/prizes/medicine/1994/rodbell/biographical/

Reporter, G. S. (2018, March 22). Professor Martin Rodbell obituary. The Guardian. https://www.theguardian.com/news/1998/dec/30/guardianobituaries

VIS SCIENCE. (2024, January 7). Martin Rodbell: Unraveling Cellular Signaling | Scientist Biography [Video]. YouTube. https://www.youtube.com/watch?v=LHJRX4hLIc0