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Lecture 16

Lecture 16 - Ch 16 and 17 - Cytoskeleton and Cell Cycle - March 12 2013.docx

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BIOL 2021
Patricia Lakin- Thomas

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March 12, 2013 Lecture 16 – Chapters 16 and 17 – Cytoskeleton, Motors and Cell Cycle Mechanoreceptors  Myosin, kinesin, dynein  Organelle Transport o Motor proteins carry organelles – minus to bring in, plus to bring out o ER Localization – Fig 12-24A  Plus end directed kinesin carry ER out o Golgi Localization – Fig 13-26  Minus end directed  Dyneins carry golg o Myosin + actin can also carry organelles Muscle Contraction  Movement with myosin and actin  Skeletal muscle – Fig 16-73  Muscle fiber – myoblasts (will make muscle)  Multinucleated cells  Myofibril is actual contractile unit – cylindrical chain – Fig 16-74  Many myofibrils in parallel – figure 16-76 o Centre is called the sarcomere – one contractile o Actin are thin filaments o Myosin are thick filaments o Actin attached at Z-disk o Contraction – sliding of myosin against actin o Z-disks get closer together  Tropomyosin o Binding to actin – going to stop the contraction as it blocks the myosin binding site  Troponin protein complex o Regulates the tropomyosin o Binds Ca2+, moving tropomyosin away o Immediately binds to actin  contraction  Sarcoplasmic reticulum (in the ER, stores Ca2+)  Action poteintial in PM o Transmitted to the T-tubule  Voltage gated Ca2+ channel opens o Ca2+ released into the cytosol, triggers release of Ca2+ from SR  more Ca2+ o Neuromuscular junction Chemotaxis  Neutrophil cells o Immune system destroys pathogens – Fig 16-4 o Cell is polarized (different on two ends) o Actin rearrangements o Actin network  ARP Activation at front causing nucleation  Disassemble network at rear o Signalling during neutrophil polarization o External signal is GPCR  Fig 16-102 o Rho family – GTPases  Ras superfam  Rho + Rac (a kind of Rho)  GPCR  GiI3Kinase  PIP3 Rac activated GEF  Rac   ARP Filamin actin webs from  Decrease myosin activity o Myosin and active are stress fibers o Local formation of actin network near activated GPCRs  PIP3 stays local o Rho: Same GPCR  G12/G13  Rho ActivationFormins  More stress fibers o Rho
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