BO101 Cell Biology Lecture 4: Cellular Signalling Notes PDF

Cellular Signalling BO101 - Cell Biology - Lecture 4 Dr Andrew Flaus, Biochemistry Reception - Transduction - Response Campbell g 9.6 fi Signal transduction pathways Reception Detection of signalling molecule binding Transduction Passage of signal along relay...

Cellular Signalling BO101 - Cell Biology - Lecture 4 Dr Andrew Flaus, Biochemistry Reception - Transduction - Response Campbell g 9.6 fi Signal transduction pathways Reception Detection of signalling molecule binding Transduction Passage of signal along relay Response Speci c biochemical change fi Indirect: Diffusible factors In yeast chemical signals identify cell type and initiate mating In bacteria chemical signals for quorum sensing enabling bio lms Campbell g 9.3 fi fi  Indirect: local v long distance paracrine endocrine local on nearby cells distant via bloodstream cell growth factors nerve impulses hormones (synaptic) (insulin) Campbell g 9.5 fi Direct: cell-cell contact In multicellular eukaryotes direct transport of chemical signals by interlinked cells, or cell-cell contacts Campbell g 9.4 fi  Receptors in plasma membrane 1 Example 1 Receptor tyrosine kinases dimerisation activates phosphorylation Campbell g 9.8 fi Receptors in plasma membrane 2 Example 2 Ligand gated ion channels ligand (effector) activates channel Campbell g 9.8 fi Receptors in plasma membrane 3 Example 3 G Protein- Coupled Receptors activate G-proteins to pass signal Campbell g 9.8 fi Signal transduction pathways Reception Detection of signalling molecule binding Transduction Passage of signal along relay Response Speci c biochemical change fi Reception - Transduction - Response Campbell g 9.6 fi  Signal transduction The linkage of a mechanical, chemical or electromagnetic stimulus to a speci c cellular response Campbell Biology glossary fi  Transduction in cytoplasm by kinases Example 1 Kinase cascades kinase enzyme adds phosphate phosphate activates next kinase ampli cation of signal Campbell g 9.10 fi fi Transduction in cytoplasm by cAMP Example 2 Second messengers Small non-protein molecule relays signal Campbell g 9.11, 9.12 fi Transduction in cytoplasm by Ca , 2+ IP3 Example 2 Second messengers Small non-protein molecule relays signal Campbell g 9.14 fi  Intracellular receptors Example Steroid hormones pass membrane, bind cytoplasmic receptors, enter nucleus to activate genes Campbell g 9.9 fi Signal transduction pathways Reception Detection of signalling molecule binding Transduction Passage of signal along relay Response Speci c biochemical change fi Response in nucleus ๏ Modify transcription factor activity ‣ Activation or repression ๏ Transcription is up or down- regulated ‣ See Control of Gene Expression Campbell g 9.15 fi Response in cytoplasm ๏ Modify activity of enzymes ‣ eg Adrenalin (epinephrine) on liver cells induces glycogen breakdown ๏ Ampli cation by catalysis ‣ 1 adrenaline = 108 glucose released from glycogen Campbell g 9.16 fi fi Combinatorial effects ๏ Signalling pathways can interact A. Single direct response B. Multiple responses from signal via branched pathways C. Cross-talk between pathways for integration of signals D. Cell-type speci city of response ๏ Complexity of cell signalling pathways Campbell g 9.17 fi fi Summary of lecture ๏ Signal transduction ‣ Short and long distances ๏ Pathway properties ‣ Reception eg RTKs, GPCRs, steroid hormone receptors ‣ Transduction eg Kinase cascade, 2nd messengers ‣ Response Transcription in nucleus Enzyme regulation in cytoplasm Learning outcomes for lecture ๏ On successful completion of this lecture, you will be able to: ‣ Explain the concept of a signal transduction pathway ‣ Name and give examples of the three stages of cell signalling ‣ Describe the contribution of cell-surface transmembrane receptors to receiving cell signals ‣ Describe the properties of kinase cascades and small molecule second messengers in signal transduction ‣ Explain how cell signalling can regulate transcription and cytoplasmic activities