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Komunikasi sel

Komunikasi sel. Sel komunikasi essential bagi organisme multiseluler Sinyal eksternal diubah menjadi respon di dalam sel. Signal transduction pathways/ jalur transduksi sinyal Sinyal pada permukaan sel dikonversi menjadi respon seluler spesifik melalui serangkaian langkah

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Komunikasi sel

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  1. Komunikasi sel

  2. Selkomunikasi essential bagiorganismemultiseluler Sinyaleksternaldiubahmenjadirespondidalamsel Signal transduction pathways/jalurtransduksisinyal Sinyalpadapermukaanseldikonversimenjadirespon selulerspesifikmelaluiserangkaianlangkah Pensinyalaninimiripbaikpada microbes (yeast) dan mamalia, tumbuhanmekanismepensinyalantelah berkembangdenganbaiksebelummahlukmultiseluler munculdibumi

  3. Komunikasi sel Selberkomunikasidenganmelepaspembawapesan (mesenjer)

  4. Lintasan transduksi sinyal • Sinyal kimia dikonversi dari satu tipe sinyal menjadi sinyal lain untuk menghasilkan molecular response. All organisms require signaling pathways to live. • Huruf mewaliki senyawa kimia atau protein. Tanda panah menunjukkan langkah enzimatik. ABCDEFG

  5. Plasma membranes Gap junctions between animal cells Plasmodesmata between plant cells Cell junctions. Both animals and plants have cell junctions that allow molecules to pass readily between adjacent cells without crossing plasma membranes. Sel hewan dan sel tumbuhan komunikasi dengan kontak langsung, memiliki cell junctions yang secara langsung menghubungkan sitoplasma dengan sel sebelahnya

  6. Cell-cell recognition. Two cells in an animal may communicate by interaction between molecules protruding from their surfaces. Pada signaling lokal pada sel hewan, dapat berkomunikasi melalui interaksi antara molekul2 yang menonjol dari permukaan sel

  7. Cara kerja cell-cell signaling Direct Pensinyalan kimiawi jarak dekat • Pensinyalan parakrin. Molekul sinyal dikeluarkan oleh sebuah sel dan bekerja pada sel target di dekatnya. Molekul pengatur lokal dilepas ke dalam fluida ekstraseluler • Pensinyalan sinaptik. Sel saraf melepaskan molekul neurotransmiter ke dalam sinapsis. Jarak yang lebih jauh • Pensinyalan hormonal. Sel endokrin mensekresi hormon ke dalam cairan tubuh (darah).

  8. Local signaling Target cell Electrical signal along nerve cell triggers release of neurotransmitter Neurotransmitter diffuses acrosssynapse Secretory vesicle Local regulator diffuses through extracellular fluid Target cell is stimulated (b) Synaptic signaling. A nerve cell releases neurotran-smitter molecules into a synapse, stimulating the target cell. (a) Paracrine signaling. A secreting cell acts on nearby target cells by discharging molecules of a local regulator (a growth factor, for example) into the extracellular fluid. • In other cases, animal cells communicate using local regulators

  9. Long-distance signaling Blood vessel Endocrine cell Hormone travels in bloodstream to target cells (c) Hormonal signaling. Specialized endocrine cells secrete hormones into body fluids, often the blood. Hormones may reach virtually all body cells. Target cell • In long-distance signaling both plants and animals use hormones

  10. Jalur lintasan bersifat inter-linked Signalling pathway Genetic network STIMULUS Metabolic pathway

  11. metabolic pathways 1993 Boehringer Mannheim GmbH - Biochemica

  12. EXTRACELLULAR FLUID CYTOPLASM Plasma membrane 1 2 3 Reception Transduction Response Receptor Activation of cellular response Relay molecules in a signal transduction pathway Signal molecule Proses percakapan seluler • Terdiridari 3 tahapan • Penerimaan • Transduksi • Respon

  13. Reception/Penerimaan: pendeteksiansinyal yang • datangdariluarselolehsel target • Sinyal yang ditransduksimemicuresponselularspesifik • Pengikatanmolekulsinyalmengubah protein reseptor • mengawaliprosestransduksi • reseptorbersifatsangatspesifik • Intracellular receptors cytoplasmic or nuclear proteins • Reseptorpada plasma membran Molekulsinyal yang menggunakanreseptoriniadalah yang kecilatau hydrophobic dandapatlangsungmelewati plasma membran

  14. Hormone (testosterone) EXTRACELLULAR FLUID 1 The steroid hormone testosterone passes through the plasma membrane. Plasma membrane Receptor protein 2 Testosterone binds to a receptor protein in the cytoplasm, activating it. Hormone- receptor complex 3 The hormone- receptor complex enters the nucleus and binds to specific genes. DNA mRNA 4 The bound protein stimulates the transcription of the gene into mRNA. NUCLEUS New protein 5 The mRNA is translated into a specific protein. CYTOPLASM Figure 11.6 • Steroid hormones • Bind to intracellular receptors

  15. Receptors in the Plasma Membrane • Terdapat tiga tipe reseptor menbran • G-protein-linked • Tyrosine kinases • Ion channel

  16. Signal-binding site Segment that interacts with G proteins Inctivate enzyme ActivatedReceptor G-protein-linked Receptor Signal molecule Plasma Membrane GDP G-protein(inactive) GTP GDP CYTOPLASM Enzyme Activated enzyme GTP GDP Pi Cellular response Figure 11.7 G-protein-linked receptors

  17. Signal-binding sit Signalmolecule Signal molecule Helix in the Membrane Tyr Tyr Tyr Tyr Tyrosines Tyr Tyr Tyr Tyr Tyr Tyr Tyr Tyr Receptor tyrosinekinase proteins(inactive monomers) Dimer CYTOPLASM Activatedrelay proteins Cellularresponse 1 Tyr Tyr Tyr Tyr Tyr Tyr P P Tyr P Tyr Tyr Tyr Tyr P Tyr Tyr Tyr P P P Tyr Tyr Tyr Tyr Tyr P Tyr Tyr Tyr Cellularresponse 2 P P P Tyr Tyr P 6 ATP 6 ADP Activated tyrosine- kinase regions (unphosphorylated dimer) Fully activated receptor tyrosine-kinase (phosphorylated dimer) Inactiverelay proteins Receptor tyrosine kinases

  18. Gate closed Signalmolecule(ligand) Ions Ligand-gated ion channel receptor Plasma Membrane Gate open Cellularresponse Gate close Figure 11.7 Ion channel receptors

  19. Lintasan transduksi sinyal • Transduksi: Jalur interaksi molekuler yang menyalurkan sinyal dari reseptor ke molekul target dalam sel • Multistep pathways • Memperbesar sinyal • Memberikan lebih banyak kesempatan untuk koordinasi dan regulasi

  20. Protein Phosphorylation and Dephosphorylation • Banyak jalur sinyal termasuk jalurphosphorylation Mekanisme utama transduksi sinyal • Dalamprosesini • Sejumlah protein kinasemenambahkanfosfat • kepada protein kinaselainnyadan • mengaktifkannya • Enzimfosfataseselanjutnyamenghilangkanfosfat

  21. Signal molecule A relay molecule activates protein kinase 1. Receptor Activated relay molecule 4 1 3 5 2 Inactive protein kinase 1 Active protein kinase 1 transfers a phosphate from ATP to an inactive molecule of protein kinase 2, thus activating this second kinase. Active protein kinase 1 Active protein kinase 2 then catalyzes the phos- phorylation (and activation) of protein kinase 3. Inactive protein kinase 2 ATP Phosphorylation cascade P Active protein kinase 2 ADP PP P i Enzymes called protein phosphatases (PP) catalyze the removal of the phosphate groups from the proteins, making them inactive and available for reuse. Inactive protein kinase 3 Finally, active protein kinase 3 phosphorylates a protein (pink) that brings about the cell’s response to the signal. ATP P ADP Active protein kinase 3 PP P i Inactive protein ATP P ADP Active protein Cellular response PP P  i A phosphorylation cascade

  22. NH2 NH2 NH2 N N N N N N N N N N N O O O N O Adenylyl cyclase Phoshodiesterase CH2 O HO Ch2 P –O O P O P P O CH2 O O O O O O O O O P Pyrophosphate H2O O O P P i OH OH OH OH OH ATP Cyclic AMP AMP Molekul kecil dan ion sebagai Second Messengers • Second messengers • Kecil, nonprotein, molekul yang larut dalam air atau berupa ions • Cyclic AMP (cAMP) terbuatdari ATP

  23. First messenger (signal molecule such as epinephrine) Adenylyl cyclase G protein GTP G-protein-linked receptor ATP cAMP Protein kinase A Cellular responses • G-proteins • Memicu pembentukan cAMP, yang kemudian berlaku sebagai second messenger dalam lintasan seluler Figure 11.10

  24. Calcium ions and Inositol Triphosphate (IP3) • Calsium, saat dikeluarkan ke dalam sitosol • Bertindak sebagai second messenger dalam berbagai jalur • Calsiumadalah second messenger yang penting • Karenaselmampumengaturkonsentrasinyadalamsitosol • Second messengers sepertiinositoltriphosphatedandiacylglycerol (DAG) dapatmemicupeningkatan • kalsiumdisitosol

  25. EXTRACELLULAR FLUID Plasma membrane Ca2+pump ATP Mitochondrion Nucleus CYTOSOL Ca2+pump Endoplasmic reticulum (ER) ATP Ca2+pump Key High [Ca2+] Low [Ca2+]

  26. 3 2 1 4 6 5 A signal molecule binds to a receptor, leading to activation of phospholipase C. DAG functions as a second messenger in other pathways. Phospholipase C cleaves a plasma membrane phospholipid called PIP2 into DAG and IP3. EXTRA- CELLULAR FLUID Signal molecule (first messenger) G protein DAG GTP PIP2 G-protein-linked receptor Phospholipase C IP3 (second messenger) IP3-gated calcium channel Endoplasmic reticulum (ER) Various proteins activated Cellularresponse Ca2+ Ca2+ (second messenger) The calcium ions activate the next protein in one or more signaling pathways. IP3 quickly diffuses through the cytosol and binds to an IP3– gated calcium channel in the ER membrane, causing it to open. Calcium ions flow out of the ER (down their con- centration gradient), raising the Ca2+ level in the cytosol.

  27. Respon sitoplasmik dan nuklear • Respon: • Cell signaling menyebabkanregulasicytoplasmic • activitiesatautranscription • Dalamsitoplasma • Jalur signaling mengaturaktivitasseluler yang bervariasi

  28. Reception Binding of epinephrine to G-protein-linked receptor (1 molecule) Transduction Inactive G protein Active G protein (102 molecules) Inactive adenylyl cyclase Active adenylyl cyclase (102) ATP Cyclic AMP (104) Inactive protein kinase A Active protein kinase A (104) Inactive phosphorylase kinase Active phosphorylase kinase (105) Inactive glycogen phosphorylase Active glycogen phosphorylase (106) Response Glycogen Glucose-1-phosphate(108 molecules) Respon sitoplasmik Figure 11.13

  29. Growth factor Reception Receptor Phosphorylation cascade Transduction CYTOPLASM Inactive transcription factor Active transcription factor Response P DNA Gene mRNA NUCLEUS • Lintasan lain • Mengatur gen dengan mengaktifkan faktor transkripsi yang meng-on dan of-kan gen

  30. Jalur signal denganbanyaktahap • Dapatmemperbesarsinyaldanberpengaruh • terhadapkekhususanrespon • Tiap protein dalamjalur signaling: • Mengamplifikasisinyaldenganmengaktifkanbanyak copy darikomponenselanjutnyadalamjalur • Kombinasi protein yang berbedadidalamsel • Memberikankespesifikan yang baikpadaseldalam • sinyal yang dideteksimaupunrsepon yang • diakibatkan

  31. Berhentinya sinyal • Respon sinyal berhenti dengan cepat • Dengan lepasnya ikatan ligan

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