Human Biology and Physiology (BMD 211) Lecture 4: Cell Communication and Signaling PDF

Human Biology and Physiology (BMD 211) Lecture 4: Cell communication and signaling Assistant Prof. Raghda Ramadan 1 Lecture 4: Cell communication and signaling I Campbell Biology, 11th edition, Chapter 11; Cell Communication, P. 212-233 3 ...

Human Biology and Physiology (BMD 211) Lecture 4: Cell communication and signaling Assistant Prof. Raghda Ramadan 1 Lecture 4: Cell communication and signaling I Campbell Biology, 11th edition, Chapter 11; Cell Communication, P. 212-233 3  4 www.simplypsychology.org/fight-flight-freeze-fawn.html Why you experienced these physiological changes? 1.Fight-or-Flight Response: In this scenario, your body undergoes a fight-or-flight response. This is the body's natural response to danger. 2.Cell Communication and Signaling: 1. Your brain detects the stressful situation and stimulate the release of stress hormones like adrenaline (also called epinephrine) and cortisol from adrenal glands, to enter the bloodstream and act on different parts of your body through cell signaling and communication pathways. 3.Physiological Changes (Response): 1. As a result of these signal molecules which are communicated between the body cells, your body experiences physiological changes. Your heart rate increases, pumping blood to your brain to help you think more clearly. 2. Your breathing quickens to supply your brain with more oxygen, and you become more alert and focused. 4.Decision: You now have a decision to make it : Do you fight through the exam by trying your best, or do you consider leaving the classroom (flight) to avoid the stress? 5 How adrenaline signals induce these effects? How are cells communicating? Lecture 4: Cell communication and signaling 6 Lecture outline 1. Cell communication in the body: Local cell-cell communication o Direct contact o Synaptic signaling o Autocrine and paracrine signals Long distance cell-cell communication o Endocrine system o Nervous system 2. Signal transduction pathway 3. Experimental design and hypothesis testing 7 Intended Learning Outcomes (ILOs) By the end of the lecture, students should be able to: Understand how local communication and long-distance communication work Describe how cell junctions, contact-dependent signals, synaptic signals, autocrine and paracrine signals mediate local communication Describe how endocrine and nervous systems mediate long distance communication Understand the principles of signal transduction pathway Describe the three stages of signal transduction pathway Understand how to generate hypothesis and to set an experimental design to test hypothesis 8 Communication in the body ❖ How cells talk to each other to keep our bodies running smoothly? The human body relies on a complex system of communication between cells to coordinate functions and maintain homeostasis (regulation of the internal environment within the body). 9 Communication in the body ❑ Cell to cell communication is the process by which cells send and receive signals to each other. It is essential for response to changes in the internal and external environment and for many body functions, including: Growth and Development Repair Metabolism Immune function ❑ Dysfunction in cell communication can lead to various diseases, including: Cardiovascular Disease Neurological Disorders Cancer Autoimmune Diseases Endocrine Disorders 10  Communication in the body ❖ How does cell to cell communication work? ✓ Sender cells: cells communicate with each other using chemical messengers released from sender cells (e.g., small molecules, hormones, neurotransmitters,..etc) ✓ Receiver cells: these messages binds to receptors on the surface of other receiver (target) cells. ✓ Response: this binding triggers a series of events inside the cells that ultimately leads to a cellular response. 11 Communication in the body ❑ A. Local communication: Occur at neighboring target cells ❑ B. Long distance communication: Responses are made at distance from original signal 12  Cell-cell communication A) Local communication 1. Direct contact Cell junctions a) Gap junction: Channels made up of transmembrane connexin proteins that link the cytoplasm of two cells together for exchange of ions, second messengers, and small metabolites (Ex: heart tissues) ▪ Gap junctions allow passage of calcium ion from cell to cell, effectively transmitting action potential across the entire heart, causing heartbeats Cell 1 Cell 2 Gap junction  Cell-cell communication A) Local communication 1. Direct contact Cell junctions b) Tight junction: watertight seal to prevent molecules and water from passing between cells (Ex: in bladder and intestine) c) Adheren Junctions: mediate cell-cell adhesion, involved in intracellular signaling (Ex: in endothelial cells) d) Desmosomes: link the cytoskeletons, allow passage of water and ions in between cells (Ex: in skin)  Cell-cell communication A) Local communication 1. Direct contact Contact-dependent signals Occurs when surface protein molecules on one cell membrane bind to surface receptor molecules on another cell’s membrane in a process called cell-cell recognition (Ex: in immune cells) Receptor protein Integral membrane protein When the integral membrane protein binds to its receptor on adjacent cell, it elicit different responses Cell-cell communication A) Local communication 2. Synaptic signaling Electrical signals are transmitted along the axon of the neurons Neurotransmitters are secreted from neurons into a small area (synapse) and diffuse to the target cell that express specific receptor to elicit the response Cell-cell communication A) Local communication 3. Autocrine and paracrine signals Autocrine signals: when secreted protein molecules acts on the receptor of the same cells Paracrine signals: when secreted protein molecules acts on the receptor of neighboring cells Autocrine and paracrine signals (local regulators) diffuse to targets through interstitial fluid Cell-cell communication A) Local communication 3. Autocrine and paracrine signals Ex: Wound healing process: when tissue is damaged, cells at the site of the wound release chemical messengers called cytokines. These cytokines, such as IL-1, IL-6, and TNF-α, diffuse to nearby cells and trigger a variety of responses, including: Inflammation: Cytokines recruit immune cells to the site of the wound to help fight infection and clean up dead cells. Cell proliferation: Growth factors such as PDGF, EGF, and FGF stimulate the growth and division of cells at the site of the wound. Angiogenesis: VEGF stimulates the growth of new blood Ex: Cytokines release from injured cells and working on vessels to the site of the wound, which is essential for the neighboring cell to start the inflammatory response delivery of oxygen and nutrients to the healing cells Cell-cell communication A) Local communication Signals to target cells in the neighboring area 2. Synaptic 3. Autocrine and 1. Direct contact signaling paracrine signals Cell 1 Cell 2  Cell-cell communication B) Long distance communication 1. Endocrine system Hormones/chemicals are secreted by endocrine cells to be circulated into the blood (Ex: insulin) Only target cells with specific receptor for the hormone will respond to signal Hormones are similar to paracrine and autocrine signal, but the key difference is that hormones travel through the blood, but autocrine and paracrine signals occur within the interstitial fluid Cell-cell communication B) Long distance communication 1. Endocrine system 2. Nervous system Neurons could also release neurohormones into the blood for action of distant target cells (similar to endocrine system) Ex: Corticotropin-releasing hormone (CRH) is produced by the hypothalamus in the brain and stimulates the adrenal glands, above the kidneys, to produce and release cortisol, which is a stress hormone and plays a role in the body's response to stress.  Cell-cell communication B) Long distance communication Signals to target cells in distant area 1. Endocrine system 2. Nervous system Hormones Neurohormones  B) Long distance communication A) Local communication 23 www.simplypsychology.org/fight-flight-freeze-fawn.html  Cell-cell communication ❖ Exosomes: Exosomes are tiny, membrane-bound vesicles that are released from cells. They contain a variety of molecules, including proteins, nucleic acids, and lipids. Exosomes are also involved in cell-cell communication either through autocrine/paracrine communication or long-distance communication. Researchers are still learning about the many ways that exosomes are used for cell-cell communication. However, it is clear that exosomes play an important role in many physiological and pathological processes (such as cancer, neurodegenerative diseases, cardiovascular diseases…etc). EX: Exosomes from cancer cells can transfer oncogenes and growth factors to other cells, to promote tumor growth and Cell-to-cell communication through exosomes and processing of metastasis. neurologic toxin proteins via exosomes. Kalani et al., Mol Neurobiol. 2014 Feb;49(1):590-600. Exosome research has challenges as well as opportunities! 27 Cell-cell communication Exosome research has challenges as well as opportunities 28  Cell-cell communication Molecular Techniques to investigate cell communication 1. Detecting and measuring the expression levels of specific genes or proteins involved in cell communication (Ex: Connexin 43 protein, the building block of gap junctions) Protein level Gene expression Connexin 43 Pannexin qPCR Western blot ELISA Fluorescence-based assays (Enzyme-Linked Immunosorbent Assay) (Imuunohistochemistry) 29  Cell-cell communication Molecular Techniques to investigate cell communication 2. Co-Culture Experiments: different cell types are cultured together, and the effects of direct cell-to-cell communication and paracrine communication can be assessed. For example, one cell type may release a signaling molecule that can be tracked by a fluorescent dye, or secreted soluble paracrine molecules can be detected by ELISA 30  Cell-cell communication Molecular Techniques to investigate cell communication 3. Scrape loading and Dye transfer: this assay assess the gap junction direct communication between adjacent cell, by inducing a scratch in cell, then incorporating fluorescent dye with molecular weight suitable to pass through gap junctions. 4. Live-Cell Imaging: Monitor the real-time behavior of cells in response to direct and paracrine signals using live-cell imaging techniques And much more … 31 Lecture outline 1. Cell communication in the body: Local cell-cell communication o Direct contact o Synaptic signaling Autocrine and paracrine signals o How does it work? Long distance cell-cell communication What happens between the binding of a o Endocrine system signaling molecule and the response? o Nervous system 2. Signal transduction pathway 32 Signal transduction pathway ❑ The process that converts a signal on a cell’s surface into a cellular response involved a series of steps that are collectively called signal transduction pathway Overview of cell signaling: From the perspective of the cell receiving the message, cell signaling can be divided into three stages: signal reception, signal transduction, and cellular response. When reception occurs at the plasma membrane, the transduction stage is usually a pathway of several steps (three are shown as an example),with each specific relay molecule in the pathway bringing about a change in the next molecule. The final 33 molecule in the pathway triggers the cell’s response.  Signal transduction pathway ❑ The process that converts a signal on a cell’s surface into a cellular response involved a series of steps that are collectively called signal transduction pathway 1. Reception ❑ The signal molecule, called ligand, (Ex: hormones) attaches to a specific receptor protein on a target cell ❑ When the signal molecule attaches, the receptor becomes activated and undergoes a conformational change (changes in its shape), which activates intracellular signal molecules. 34  Signal transduction pathway ❑ The process that converts a signal on a cell’s surface into a cellular response involved a series of steps that are collectively called signal transduction pathway 1. Reception 2. Transduction ❑ The transduction stage converts the signal to a specific cellular response ❑ Transduction sometimes occurs in a single step but more often requires a sequence of changes in a series of different molecules ❑ Relay molecule(s) become activated and start a series of reactions (a cascade) in the cytoplasm that may amplify signals (i.e; these reactions get more intense at each step) 35  Signal transduction pathway ❑ The process that converts a signal on a cell’s surface into a cellular response involved a series of steps that are collectively called signal transduction pathway 1. Reception 2. Transduction 3. Response ❑ The final molecule in the signal transduction pathway will lead to a nuclear response and/or a cytoplasmic response within the cell ❑ (Eg: Regulate gene expression in the nucleus, activate an enzyme to catalyze a specific chemical reaction (for example, glycogen phosphorylase, as a 36 response to fight-flight status) Signal transduction pathway What happens between the binding of a signaling molecule and the response? Lecture 5: Cell signaling II 37 (Mechanisms of cell signaling ) Signal transduction pathway In this signaling system, the hormone epinephrine (adrenaline) acts through a G protein-coupled receptor to activate a succession of relay molecules, including cAMP and two protein kinases (see Figure). The final protein activated is the enzyme glycogen phosphorylase, which uses inorganic phosphate to release glucose monomers from glycogen in the form of glucose 1-phosphate molecules. This pathway amplifies the hormonal signal: One receptor protein can activate approximately 100 molecules of G protein, and each enzyme in the pathway, once activated, can act on many molecules of its substrate, the next molecule in the cascade. Lecture 5: Cell signaling II 38 (Mechanisms of cell signaling ) Signal transduction pathway ❖ Most cells combine intracellular signaling with intercellular signaling Cell 1 Cell 2 intracellular signaling (inside cells) intercellular signaling (between cells) 39 Signal transduction pathway 40 Cell communication and signaling References 1. Campbell Biology, 11th edition, Chapter 11; Cell Communication, P. 212-233 2. Molecular Biology of the Cell, 6th edition, Chapter 15: Cell Signaling. P. 813 -888 https://www.youtube.com/watch?v=-dbRterutHY&t=335s 41 Applications! Lecture outline 1. Cell communication in the body: Local cell-cell communication o Cell junction o Contact-dependent signals o Autocrine and paracrine signals Long distance cell-cell communication o Endocrine system o Nervous system 2. Signal transduction pathway 3. Experimental design and hypothesis testing 43 Experimental design and hypothesis testing ❑ Scientific research Experimental design and hypothesis testing Background knowledge and Breast Cancer is the most common cancer in women worldwide problem description  Experimental design and hypothesis testing Background knowledge Radiotherapy is a standard therapy for breast cancer treatment after conservative surgery and and mastectomy (>60% receive Radiotherapy) problem description Radiation Cancer Cardiovascular system is Radiation exposed to radiation (higher exposure for left-sided breast cancer) Breast cancer Radiotherapy samsunghospital.com Side effects: Radiation-induced cardiovascular diseases, especially atherosclerosis (10-15 years after Radiotherapy)  Experimental design and hypothesis testing Background Currently, there is no radioprotective compound against potential atherosclerotic knowledge complications after breast cancer radiotherapy. and problem description Process of radioprotective drug development Understanding Identifying potential Developing drugs molecular mechanisms molecular targets (Radioprotectants) Experimental design and hypothesis testing Background Atherosclerosis knowledge and problem Ca2+ description LDL Inflammation Oxidative stress overload http://cliparts.co/cliparts/kc8/k9a/kc8k9ajri.jpg Damaged endothelium Encyclopedia Britannica, Inc. Endothelium Smooth muscle cells Foam cells Fibrous cap Lipid, calcium, Smooth muscle debris Damaged endothelium and Healthy artery formation of atherosclerotic plaque Endothelial cell dysfunction is the first event in the atherosclerotic process  Experimental design and hypothesis testing Background knowledge Radiation-induced Atherosclerosis and problem description Senescence DNA damage Encyclopedia Britannica, Inc. Endothelial cell Endothelial cell Cardiovascular system Cell death Inflammation Oxidative stress Endothelial cell dysfunction is the first event in the atherosclerotic process Experimental design and hypothesis testing ❑ Scientific research  Experimental design and hypothesis testing DNA damage Senescence Radiation-induced Atherosclerosis Formulate hypothesis Endothelial cell Endothelial cell Cardiovascular Cell death system Inflammation Oxidative stress Cell communication Gap junction Endothelial cell dysfunction is the first Irradiated cell Hemichannel event in the atherosclerotic process Connexin Connexin Non-irradiated cell Experimental design and hypothesis testing ❑ Scientific research  Experimental design and hypothesis testing What is the effect of Single/fractionated X-rays Radiation on cell (0 Gy- 0.1 Gy- 0.5Gy- 5 Gy) communication? Hypothesis testing Gap junction Hemichannel Experimental model Composed of Connexin Coronary artery/Microvascular proteins (Cx) Endothelial cell (EC) Experimental work to test the hypothesis proatherogenic Cx43 Atheroprotective Cx40 Gene & protein expression Gene & protein expression Positive & Negative controls Gap junction communication Dye uptake ATP release ATP Cx43 Hemichannel opening (pathological condition) Experimental design and hypothesis testing What is the effect of Single/fractionated X-rays Radiation on cell (0 Gy- 0.1 Gy- 0.5Gy- 5 Gy) communication? Hypothesis testing Gap junction Hemichannel Results Composed of Connexin Coronary artery/Microvascular proteins (Cx) TIC A E C x4 0 Endothelial cell (EC) 1.5 0.1 G y TIC A E C x4 3 0.5 G y 2.5 ** R e la tiv e a m o u n t C x 4 0 / V in c u lin 0.1 G y 1.0 5 Gy ** * * * ** ** 2.0 ** 0.5 G y * ** * R e la tiv e a m o u n t * * ** ** C x 4 3 / V in c u lin * * * 5 Gy 1.5 ** * * ** * ** ** 0.5 ** ↑ proatherogenic Cx43 ↓ Atheroprotective Cx40 1.0 ** 0.5 Gene & protein expression Gene & protein expression 0.0 0.0 h h h d h d 4 8 2 4 6 7 h h h h d d 2 4 7 1 6 4 8 2 7 4 2 4 7 1 T im e P o in t a fte r ir r a d ia tio n T im e P o in t a fte r ir r a d ia tio n G J c o m m u n i c a t i o n 7 2 h p. i. 2.0 ** 1.5 R e la t iv e a r e a ** 1.0 0.5 0.0 ↑ Gap junction communication y y y G G G.1 0 5 GJ and HC are involved in IR-induced 0 H e m ic h a n n e l o p e n in g 7 2 h p.i P I p o s itiv e - D e x t r a n n e g a tiv e / c e ll c o u n t 3 bystander effect 0 Gy ** 0.1 G y ↑ transfer of damaging 2 * 5 Gy signals related to IR ↑ risk of EC damage    1 ↑ Cx43 Hemichannel opening (pathological condition) 0 L 9 R 1 T p C a -G T A T  Experimental design and hypothesis testing How alteration in cell communication contributes to cell damage? ROS X-irradiation of ECs How does it work? Apoptosis Ca+2 Inflammation ATP Senescence P2X7 ROS/RNS P2X7 Cx43 HC Ca+2 Channel opening Na+ Swelling IL-1B IL-6 Glutathione Signal pathway SOD MCP-1 PI3k/AKT IL-8 Inflammation Ca+2 ROS NF-KB overload Inflammation VCAM-1 P38 MAPK Caspases Apoptotic signals Endothelin-1 DNA damage GDF-15 NLPR3 SASP Apoptosis ATP IL-1B ROS DAMP IL-6 TNF-a - ATP depletion cause mitochondrial failure→ cell death - Membrane depolarization leads to loss of cell essential metabolite→ cell death - Less antioxidants→ ROS→ cell death Experimental design and hypothesis testing Do the results support hypothesis? Bioinformatic support Too many data !!! Data integration to support the conclusion Experimental design and hypothesis testing ❑ Scientific research Experimental design and hypothesis testing ❑ Scientific research Experimental design and hypothesis testing Process of radioprotective drug development Application of the finding New research questions!! Radiation induces hemichannel opening Does blocking hemichannels protects from endothelial damage?  ❑X-ray crystallography Next lecture ! https://www.khanacademy.org/science/ap-biology/cell-communication-and-cell- https://www.khanacademy.org/science/ap-biology/cell-communication-and-cell- cycle/changes-in-signal-transduction-pathways/v/g-protein-coupled-receptors cycle/changes-in-signal-transduction-pathways/v/example-of-signal-transduction-pathway 60 60