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Cytoskeleton

Cytoskeleton

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Cytoskeleton

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  1. Cell Migration and Adhesion Cytoskeleton Team Members Marta Bechtel Christine Hohmann Cleo Hughes-Darden John Navaratnam Kenneth Samuel Dayalan Srinivasan Erika Whitney Facilitators Randy Phillis Melissa Zwick

  2. Background Information • Class Level: Intermediate Cell Biology • Student Homework Before Class: • - Complete a reading assignment • - Complete an on-line quiz • (please see handout for quiz)

  3. Learning Goal & Outcome Goal: Understand the role of the cytoskeleton in cell migration & adhesion. Outcome: Students will be able to predict the effects of cytoskeletal changes on cell migration & adhesion.

  4. Why do cells move? • Normal Tissue Development • Wound Healing • Normal Cell Function Are there situations when cells move when they should not? Metastasis

  5. B A • To move the boat to the RIGHT • Remove anchor A • Remove anchor B

  6. Focal Adhesions: cellular anchors to the extracellular space extracellular space (outside) extracellular matrix (ECM) proteins integrins cell membrane adaptor complex cytoplasm (inside) Rho GTPases actin filament cuts actin filaments direction of myosin pulling LIM kinase X myosin II cofilin

  7. Focal Adhesions: cellular anchors to the extracellular space Outside of Cell extracellular matrix (ECM) proteins 3) integrins lose attachment! cell membrane adaptor complex adaptor complex 2) lack of tension along actin! cytoplasm (inside) Rho GTPase actin filament actin filament Rho GTPase 1) Cuts actin filaments LIM kinase LIM kinase Cofilin Cofilin direction of myosin pulling myosin II

  8. A - trailing edge B- leading edge direction of cell migration Which side of the cell would you predict cofilin to be most active? (A or B)

  9. What happens if cofilin cuts actin filaments at the “leading edge” of the cell? • Cell stops migration • Cell starts migration • Cell re-attaches to the Extracellular Matrix (ECM)

  10. Which of the following mimics the effect of cofilin activity on cell-ECM adhesion: Separation of Integrin from the ECM Activation of LIM Kinase Elimination of Myosin II : Actin interaction A, B, C A and C

  11. Homework • Cilengitide is a drug that is thought to act by interfering with the binding of specific integrin proteins to extracellular matrix proteins. • It has been shown to be effective in treating breast cancer. • Using the diagram for cell motility, how do you think cilengitide may affect breast cancer cells?

  12. Group (or homework) question # 2 Based on the model, you decide to use (interference) RNAi to reduce the function of the following genes. Predict the effects of each RNAi treatment on the activity of cofilin. Answer = “active” or “inactive”. • LIM kinase • Rho GTPase • Myosin II

  13. Open ended discussion question The actin filaments in the cytoskeleton are critical for cell motility in normal and cancer cells. Conversion of cofilin from inactive to active is regulated by phosphorylation:dephosphorylation. When cofilin is phosphorylated, it becomes inactivated. What is a likely outcome of the following on cell motility? • Blocking cofilin Phosphorylation • Enhancing cofilin Phosphorylation • Blocking the activity of LIMKinase

  14. When integrins bind to the ECM to the leading edge of a mobile cell, which of the following occur? A) true, B) false Cofilin is active Actin filaments are not cleaved LIM kinase is inhibiting cofilin activity Cells are able to migrate

  15. Cofilin