1. Online Counseling Resource YCMOU ELearning Drive… School of Architecture, Science and Technology Yashwantrao Chavan Maharashtra Open University, Nashik – 422222, India

2. OC-SBT082-U01-02 Introduction Programmes and Courses  SBT082 –CP01 - Unit 01

3. School of Science and Technology, Online Counseling Resource… © 2008, YCMOU. All Rights Reserved.3 Credits  Academic Inputs by Arun Punaji More. M.Sc. (Microbiology) ‏ Experience: 11 Years arunmesh@hotmail.com

4. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.4 How to Use This Resource  Counselor at each study center should use this presentation to deliver lecture of 40-60 minutes during Face-To-Face counseling.  Discussion about students difficulties or tutorial with assignments should follow the lecture for about 40-60 minutes.  Handouts (with 6 slides on each A4 size page) of this presentation should be provided to each student.  Each student should discuss on the discussion forum all the terms which could not be understood. This will improve his writing skills and enhance knowledge level about topics, which shall be immensely useful for end exam.  Appear several times, for all the Self-Tests, available for this course.  Student can use handouts for last minutes preparation just before end exam.

5. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.5 Learning Objectives  After studying this module, you should be able to: Describe the organizations of actin filaments Describe the mechanisms by which the actin filaments cause movements by cells Describe various functions of actin filaments

6. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.6 Introduction  Locomotion is essential for the survival of the animals.  The locomotion is achieved by the skeleton muscles of the body.  The movement of these skeleton muscles and other types of muscles is caused by movement of actin filaments with the help of motor molecules such as myosin proteins.  In this presentation we will learn how the actin filaments achieve this.

7. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.7 Actin Filaments-1  The actin filaments are made of with globular proteins called as actin proteins.  They are dynamic structures and keep assembling and dissembling forming bundles, meshwork of actin filaments.  The actin proteins are globular proteins and act as monomers in the formation of actin filaments.  The actin protein has got two binding sites that can associate with other actin monomers in head-to-tail interaction forming actin filaments.

8. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.8 Actin Filaments-2  The actin protein has got polarity and referred to as +ends and – ends.  The polymerization of these actin proteins leads to the formation of actin filaments which are utilized further to produce actin bundles and actin network.  The polymerization of actin proteins is initiated and regulated by actin binding proteins.  Polymerization of actin proteins is energy dependent process requiring ATP as energy molecules.

9. School of Science and Technology, Online Counseling Resource… Actin Filaments-3  Polymerization of actin proteins into actin filaments:-

10. School of Science and Technology, Online Counseling Resource… Actin Filaments-4  Branching of actin filaments:- Arp2/3 actin binding proteins and ATP molecules play actin role in Branching of actin filaments.

11. School of Science and Technology, Online Counseling Resource… Actin Filaments-4  Cytokinesis:- The actin filaments cause daughter cell Separation at the end of mitosis, a process Known as Cytokinesis.

12. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.12 Actin Filaments-3  The actin binding proteins are Arp2/3 complex:  These proteins are involved in formation of branched actin filaments ADF/cofilin proteins:  These proteins bind to the actin filaments and cause dissociation of the actin monomers Profilin proteins:  They cause association of actin monomers forming the actin filaments.

13. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.13 Actin Filaments-4  Actin bundles formation:- After the polymerization of actin proteins into the actin filaments, these filaments are reorganized into actin bundles and actin meshwork in the cytoplasm. Actin bundles formation is caused by cross linking the actin filaments by Actin-bundling proteins.

14. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.14 Actin Filaments-5  Actin-bundling proteins:- Fimbrins:  It 68 kd proteins with two binding sites for actin filaments.  It form compact actin filament bundles by binding actin filament very close together. Alpha actinin:  The alpha actinin cross links the actin filaments with greater space in between the two consecutive actin filaments which make the myosin proteins binding to the cross linked individual filament possible.

15. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.15 Actin Filaments-6  Actin-bundling proteins:-  The alpha actinin form the contractile bundles.  Since the binding of the myosin proteins to the individual actin filaments in the bundle cause the movement in the filaments in the bundles. Filamin: they are actin-binding proteins.  Filamin is dimer of two large protein subunits that cross link actin filaments forming orthogonal network of actin filaments.

16. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.16 Actin Filaments-7  The actin filaments form dense bundles beneath the plasma membrane of the cell.  This actin network and its associated actin binding proteins give cell its peculiar shape and is also involved in other cell surface activities.  This actin network beneath the plasma membrane is called as cortical cytoskeleton.

17. School of Science and Technology, Online Counseling Resource… Actin Filaments-8  Actin filaments bundles and networks:-

18. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.18 Actin Filaments-8  The cortical cytoskeleton is linked to plasma membrane by various special proteins molecules such as ankyrin, filamin, spectrin, protein 4.1, glycophorin in case of erythrocytes and other types of cells.

19. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.19 Actin Myosin Association-1  The actin filaments and myosin proteins form contractile assembly responsible for the movement of skeleton muscle.  The myosin molecules produce contraction in skeleton muscles by sliding the actin filaments relative to one another.  The actin filaments play active role in forming contact with adjacent cells, tissues and substrate through a specialized region in the plasma membrane.

20. School of Science and Technology, Online Counseling Resource… Actin Myosin Association-2  Myosin motor protein cause the sliding movements of actin filaments against each other as shown below.

21. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.21 Functions of Actin Filaments-1  The actin filaments play active role in forming contact with adjacent cells, tissues and substrate through a specialized region in the plasma membrane.  For example fibroblast cells secret extracellular matrix proteins that stick to the surface of adjacent cell or tissues or a substrate(such as culture plate surface); fibroblast then attaches to this extracellular matrix.

22. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.22 Functions of Actin Filaments-2  fibroblast then attaches to this extracellular matrix through trans membrane proteins called as integrins which are attached to the actin filament bundles called as stress fibers on the plasma membrane side.  Actin filaments are actively involved in cell-to-cell contact called as adherens junction forming sheet of cells called as adhesion belt.

23. School of Science and Technology, Online Counseling Resource… What We Learn…  Structure of Actin Filament  Polymerization of actin filaments  Motor proteins associated with actin filaments.  Functions of actin filaments

24. School of Science and Technology, Online Counseling Resource… Critical Thinking Question  Which characteristics make actin filaments useful for number of cell behaviors?

25. School of Science and Technology, Online Counseling Resource… Hints For Critical thinking Question  Dynamic nature  Movement with help of motor proteins  Formation of bundles and networks.

26. School of Science and Technology, Online Counseling Resource… © 2008, YCMOU. All Rights Reserved.26 Study Tips  Book Title: Title:The Cell, A Molecular Approach Author: Geoffrey M. Cooper, Robert E. Hausman Publication: ASM press, Washington,D.C. Publication: ASM press, Washington,D.C.  Book Title: Cell and Molecular Biology Title: Cell and Molecular Biology Author: E.D.P. De Robertis and E.M.F. De Robertis, Jr. Author: E.D.P. De Robertis and E.M.F. De Robertis, Jr. Publication: Lippincott and Williams & Wilkins Publication: Lippincott and Williams & Wilkins

27. End of the Presentation Thank You !