celltocellcommunication-101021235148-phpapp01.ppt
- 1. Cell to Cell Communication
- 2. 2 Cell to Cell Communication Communication between cells requires: ligand: the signaling molecule receptor protein: the molecule to which the receptor binds -may be on the plasma membrane or within the cell
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- 4. 4 Cell Communication There are five basic mechanisms for cellular communication: 1. Direct contact 2. Paracrine and Autocrine signaling 3. Endocrine signaling 4. Synaptic signaling
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- 6. 6 Cell Communication When a ligand binds to a receptor protein, the cell has a response. signal transduction: the events within the cell that occur in response to a signal Different cell types can respond differently to the same signal.
- 7. 7 Cell Communication A cell’s response to a signal often involves activating or inactivating proteins. Phosphorylation is a common way to change the activity of a protein. protein kinase – an enzyme that adds a phosphate to a protein phosphatase – an enzyme that removes a phosphate from a protein
- 8. Three Stages of Signal Transduction 1. Reception of extracellular signal by cell 2. Transduction of signal from outside of cell to inside of cell—often multi-stepped Note not necessarily transduction of ligand 3. Cellular Response Response is inititiated and/or occurs entirely within receiving cell
- 9. Three Stages of Signal Transduction
- 10. Three Stages 2a. Transduction 2b. Transduction 2c. Transduction 2d. Transduction 1. Reception 3. Response Responses usually involve increasing or decreasing some Protein’s Function
- 11. Three Stages 2a. Transduction 2b. Transduction 1. Reception 3. Response
- 12. 12 Receptor Types Receptors can be defined by their location. intracellular receptor – located within the cell cell surface receptor or membrane receptor – located on the plasma membrane to bind a ligand outside the cell
- 13. 13 Receptor Types There are 3 subclasses of membrane receptors: 1. channel linked receptors – ion channel that opens in response to a ligand 2. enzymatic receptors – receptor is an enzyme that is activated by the ligand 3. G protein-coupled receptor – a G- protein (bound to GTP) assists in transmitting the signal
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- 16. 16 Intracellular Receptors steroid hormones -have a nonpolar, lipid-soluble structure -can cross the plasma membrane to a steroid receptor -usually affect regulation of gene expression An inhibitor blocks the receptor from binding to DNA until the hormone is present.
- 17. 17 Intracellular Receptors A steroid receptor has 3 functional domains: 1. hormone-binding domain 2. DNA binding domain 3. domain that interacts with coactivators to affect gene expression
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- 19. 19 Receptor Kinases Receptor tyrosine kinases -membrane receptor -when bound by a ligand, the receptor is activated by dimerization and autophosphorylation -activated receptor adds a phosphate to tyrosine on a response protein -an example is the insulin receptor
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- 22. 22 Receptor Kinases kinase cascade – a series of protein kinases that phosphorylate each other in succession -amplifies the signal because a few signal molecules can elicit a large cell response mitogen-activated protein (MAP) kinases are activated by kinase cascades
- 23. 23 G-Protein Coupled Receptors G-protein – protein bound to GTP G-protein-coupled receptor (GPCRs) – receptors bound to G proteins -G-protein is a switch turned on by the receptor -G-protein then activates an effector protein (usually an enzyme)
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- 25. 25 G-Protein Coupled Receptors Once activated, the effector protein produces a second messenger. -second messenger generates the cellular response to the original signal For example – one common effector protein is adenylyl cyclase which produces cAMP as a second messenger. Other second messengers: inositol phosphates, calcium ions (Ca2+)
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- 27. 27 Cell-to-Cell Interactions Cells can identify each other by cell surface markers. -glycolipids are commonly used as tissue- specific markers -major histocompatibility complex (MHC) proteins are used by cells to distinguish “self” from “non-self”
- 28. 28 Cell-to-Cell Interactions Cells within a tissue are connected to each other by cell junctions 1. tight junctions – create sheets of cells 2. anchoring junctions – connect the cytoskeletons of adjacent cells 3. communicating junctions – permit small molecules to pass between cells - gap junctions
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