2025.2.5+BIOL+170+Cytoskeleton_+Dynamics_POST

Introduction to Actin and Myosin

  • Game Time Session

    • Join at slido.com, Session #: 7861160

    • Starts at 12:00 PM

Actin and Myosin Structure

  • Monomeric Form of Actin

    • Important to identify the basic building block of filament formation.

  • Lag Phase in Actin Assembly

    • Understanding reasons for delay in assembly during in vitro conditions.

  • Orientation within Muscle Sarcomere

    • Plus end of actin filaments capped within sarcomeres.

  • Myosin Domain

    • Myosin's ATPase activity situated in its specific domain.

  • Filament Orientation

    • Actin filaments arranged with particular end orientations towards the M-line.

Muscle Dynamics and Calcium Interaction

  • Tropomyosin and Calcium in Smooth Muscle

    • Increased cytosolic calcium causes conformational changes in tropomyosin, exposing binding sites for myosin.

    • True/False Question to reinforce learning.

  • Functional Equivalent of Z Disk in Smooth Muscle

    • Identification of structures performing similar functions in smooth muscle compared to striated muscle.

Actin-Myosin Contraction and Cell Functions

  • Actin-Myosin Interaction Beyond Contractility

    • Actin-myosin interactions play diversified roles beyond muscle contraction.

  • Myosin Supergene Family

    • Role in movement of vesicles along actin; myosins walk toward filament plus ends while carrying cargo.

Actin Structures and Cellular Functions

  • F-actin Bundles

    • Provide structural support for specialized functions, such as microvilli in epithelial cells, which increase surface area.

    • Bundled by accessory proteins including Fimbrin and Villin.

Learning Objectives Overview

  • Understand the regulation of actin-binding proteins and actin dynamics to facilitate cell motility.

    • Principles involving balance of polymerization and retrograde flow.

Actin Dynamics and Cell Movement

  • Cortical Cytoplasm Regulation

    • Differentiation between gel and sol states in the actin cortex and their implications on cell movement.

  • Actin Regulation Mechanisms

    • Factors governing transitions between solid-like and liquid-like behavior of actin.

Actin Polymerization and Dynamics

  • Dynamics of Actin Assembly

    • Recall that assembly occurs in a defined directionality (minus to plus).

  • Actin-binding Proteins

    • Gelsolin, Cofilin, and their roles in severing and capping actin filaments to regulate dynamics.

  • Reservoir of G-actin Subunits

    • Maintenance of available subunits for polymerization is crucial for consistent actin assembly.

Actin-Binding Protein Regulation

  • Types of Actin-Binding Proteins

    • Families and their roles: tropomyosin, formin, Arp 2/3, gelsolin, prevalentin functions in the cytoskeleton.

  • Mechanisms of Regulation

    • The role of Thymosin and Profilin in preventing or promoting polymerization at the actin plus end.

Cell Motility Mechanisms

  • Cell Motility Steps

    • Overview of protrusion, attachment, tension, and retraction in cell movement.

  • Dynamic Instability of Microtubules

    • Understand how microtubules alternate between growth and breakdown affecting cell structure.

Intermediate Filaments and Their Functions

  • Structure and Purpose

    • Intermediate filaments function structurally, resistant to cell stress, and contribute to cellular integrity.

Microtubule Biology

  • Structure and Assembly

    • Microtubules made from tubulin; understanding of polarity and roles during mitosis and intracellular transport.

  • Diversity of Accessory Proteins

    • MAPs influence microtubule function and organization, highlighting their importance in neuronal axon structure.

Motor Proteins and Cellular Transport

  • Kinesins and Dyneins

    • Mechanistic functions of these proteins in anterograde and retrograde transport along microtubules.

  • Dynein-Microtubule Interaction in Localization

    • Specific roles in vesicle transport, including implications for neuronal function.

Summary of Learning Objectives and Key Questions

  • Actin-Binding Proteins' Role in Cell Function

    • Comprehensive overview of actin-binding protein functions and their biological significance in cellular dynamics.