St. George's University FTM Lecture 1 - Histology of the Cytoskeleton of the Cell PDF

Basic Principles of Medicine 1 Module: Foundation to Medicine | Lecture 1 Histology of the Cytoskeleton of the Cell Dr. Mai [email protected] Department of Anatomical Sciences School of Medicine, St. George’s...

Basic Principles of Medicine 1 Module: Foundation to Medicine | Lecture 1 Histology of the Cytoskeleton of the Cell Dr. Mai [email protected] Department of Anatomical Sciences School of Medicine, St. George’s University  Copyright All year-1 course materials, whether in print or online, are protected by copyright. The work, or parts of it, may not be copied, distributed, or published in any form, printed, electronic, or otherwise. As an exception, students enrolled in year 1 of St. George’s University School of Medicine and their faculty are permitted to make electronic or print copies of all downloadable files for personal and classroom use only, provided that no alterations to the documents are made and that the copyright statement is maintained BPM1 | FTM| Lecture 1 | Histology of the Cytoskeleton of the Cell in all copies. ‘View only’ files, such as lecture recordings, are explicitly excluded from download, and creating copies of these recordings by students and other users is strictly illegal. The author of this document has made the best effort to observe current copyright law and the copyright policy of St. George's University. Users of this document identifying potential violations of these regulations are asked to bring their concerns to the attention of the author.  Your Objectives will show here! Objectives List the three domains of cellular life. SOM.MK.I.BPM1.1.FTM.3.HCB.0028 List the three major types of protein filaments that form the cytoskeleton. SOM.MK.I.BPM1.1.FTM.3.HCB.0029 State the function(s) of the three cytoskeletal elements (microtubules, intermediate filaments and microfilaments). SOM.MK.I.BPM1.1.FTM.3.HCB.0030 Describe the structure of the three cytoskeletal elements (microtubules, intermediate filaments and microfilaments). SOM.MK.I.BPM1.1.FTM.3.HCB.0031 Describe the assembly of the three cytoskeletal elements (microtubules, intermediate filaments and microfilaments). SOM.MK.I.BPM1.1.FTM.3.HCB.0032 Discuss three compounds that can affect microtubule function. SOM.MK.I.BPM1.1.FTM.3.HCB.0033 Discuss two compounds that can affect microfilament function. SOM.MK.I.BPM1.1.FTM.3.HCB.0034 BPM1 | FTM| Lecture 1 | Histology of the Cytoskeleton of the Cell State the function(s) of the centrosome. SOM.MK.I.BPM1.1.FTM.3.HCB.0035 Describe the structure of the centrosome. SOM.MK.I.BPM1.1.FTM.3.HCB.0036 Give the location of the basal body. SOM.MK.I.BPM1.1.FTM.3.HCB.0037 State the function(s) of the basal body. SOM.MK.I.BPM1.1.FTM.3.HCB.0038 Describe the structure of the basal body. SOM.MK.I.BPM1.1.FTM.3.HCB.0039 Differentiate between the following apical specializations based on function, places found and the microanatomical structures: SOM.MK.I.BPM1.1.FTM.3.HCB.0040 primary cilia, motile cilia and flagella. Differentiate between the following apical specializations based on function and the microanatomical structures: microvilli, SOM.MK.I.BPM1.1.FTM.3.HCB.0041 stereocilia. Describe the terminal web. SOM.MK.I.BPM1.1.FTM.3.HCB.0042 Describe the motor protein associated with microfilaments. SOM.MK.I.BPM1.1.FTM.3.HCB.0043 Describe the two motor proteins associated with microtubules. SOM.MK.I.BPM1.1.FTM.3.HCB.0044 Describe role of the cytoskeleton in intracellular transport. SOM.MK.I.BPM1.1.FTM.3.HCB.0045 Describe role of the cytoskeleton in cellular motility. SOM.MK.I.BPM1.1.FTM.3.HCB.0046 Describe the three types of membrane protrusion structures. SOM.MK.I.BPM1.1.FTM.3.HCB.0047 Describe the role of actin polymerization in membrane protrusion and motility, and explain how a cell moves across a substrate SOM.MK.I.BPM1.1.FTM.3.HCB.0048 by utilizing this concept. Describe the five types of intracelluar inclusions. SOM.MK.I.BPM1.1.FTM.3.HCB.0061  Recommended Reading *Material covered in lecture handout Histology – A Text and Atlas Pawlina 9th Edition Chapter 2: Cell Cytoplasm Pg. 62-81, Chapter 3: The Cell Nucleus Pg. 82-105 BPM1 | FTM| Lecture 1 | Histology of the Cytoskeleton of the Cell https://premiumbasicsciences.lwwhealthlibrary.com/content.aspx?sectionid=257424028&booki d=3290 Lippincott's Illustrated Reviews: Cell & Molecular Biology 3e Chandler & Viselli 2024 Chapters 4 https://premiumbasicsciences.lwwhealthlibrary.com/content.aspx?sectionid=255703694&bookid=324 4  Important note Some of the slides provided in this handout will have a green background BPM1 | FTM| Lecture 1 | Histology of the Cytoskeleton of the Cell This is information that will help you understand the lecture material but will NOT be covered during the lecture delivery  Terminology Cytoskeleton – a network of proteins that provide scaffolding or allow movement for the structures inside the cell Polymerization – the process by which cytoskeletal filaments are formed and lengthened through assembly of their protein subunits Treadmilling – continual process of assembly on one end and disassembly on the other to maintain the optimal length of the cytoskeletal filament BPM1 | FTM| Lecture 1 | Histology of the Cytoskeleton of the Cell Mitosis – cell division resulting in two cells identical to the original Axoneme – the central portion (core) of cilia, flagella and primary cilia Apical surface of cell – the portion of the cell that is not attached to anything also referred to as the free surface Basal surface of cell – the portion of the cell that is attached to the basement membrane Lateral surfaces of cell – the surfaces of the cell that are adjacent to other cells Terminal web – a network of actin filaments that sit just deep to the plasma membrane Signaling molecule – a substance that can be recognized by cell surface receptors and serve as a way for cells to communicate with each other Receptor – a protein that is capable of binding to a signaling molecule. May be part of the cell membrane or in the cytosol  SOM.MK.I.BPM1.1.FTM.3.HCB.0028 Cellular domains of life Eukaryotes Prokaryotes BPM1 | FTM| Lecture 1 | Histology of the Cytoskeleton of the Cell Single celled organisms Multicellular organisms Small amount of DNA Cells contain nucleus – for Plasmids for adaptation DNA No nucleus or organelles Contain organelles with E.g. specific functions Bacteria Cells are adapted to specific Archaea - extremophiles function as part of the whole  What we will cover! Quick look at the components of the cell Detailed look at Cytoskeletal elements of the cell Structure BPM1 | FTM| Lecture 1 | Histology of the Cytoskeleton of the Cell Formation Function Why is this important?  Eukaryotic cell – overview Plasma membrane - Outermost organelle which keeps everything together, also surrounds most organelles Cytoplasm – Everything on the intracellular aspect of the plasma membrane BPM1 | FTM| Lecture 1 | Histology of the Cytoskeleton of the Cell Cytoplasmic matrix (cytosol) – aqueous gel containing molecules of different size where the physiological processes of the cell takes place Cytoskeleton – polymerized proteins that serve as a framework for cell structure and organization, allows for movement within the cell and the cell itself. Determines the fluidity of the cytosol and plays an important part in cell division Organelles – little organs Inclusions – accumulations in cells byproducts of metabolism  Why study cells? Ingestion and All functions associated with life happens at absorption of a cellular level metabolites Digestion and excretion of wastes Each organelle has a function within the cell Reproduction BPM1 | FTM| Lecture 1 | Histology of the Cytoskeleton of the Cell Organelle numbers and location determines Protection cell function Movement Death Each cell has a particular function within a tissue Each tissue type has a function in the organ Each organ has a function as part of a system Nothing in the cell happens by chance  SOM.MK.I.BPM1.1.FTM.3.HCB.0029 Cytoskeleton - Overview Framework for cell structure and organization, allows for movement within the cell and the cell itself. Determines the fluidity of the cytosol and plays an important part in cell division. Microtubules Intermediate filaments Microfilaments BPM1 | FTM| Lecture 1 | Histology of the Cytoskeleton of the Cell (actin filaments)  SOM.MK.I.BPM1.1.FTM.3.HCB.0030, SOM.MK.I.BPM1.1.FTM.3.HCB.0031, SOM.MK.I.BPM1.1.FTM.3.HCB.0032 Microtubules Hollow cylindrical tubes - 25 nm diameter Have +ve and –ve charged ends = polar Consist of round (globular) protein units (α- and β- Tubulin) 13 linear protofilaments form 1 microtubule BPM1 | FTM| Lecture 1 | Histology of the Cytoskeleton of the Cell Grow from the microtubule organizing center (MTOC) by polymerization Requires ENERGY (GTP) Functions Intracellular transport Forms the mitotic spindle for cell division Control chromosomal movement Form flagella and cilia Tau proteins bind to tubulins promoting microtubule assembly and stability  SOM.MK.I.BPM1.1.FTM.3.HCB.0030, SOM.MK.I.BPM1.1.FTM.3.HCB.0031, SOM.MK.I.BPM1.1.FTM.3.HCB.0032 Microtubule organizing center (MTOC) Centrosome surrounded by protein matrix (pericentriolar material) Close to the nucleus BPM1 | FTM| Lecture 1 | Histology of the Cytoskeleton of the Cell Nucleation sites for microtubules Gamma-tubulin ring complexes on the pericentriolar material Initiate microtubule formation (polymerization) Microtubule detaches once fully assembled α- Tubulin Tubulin dimer β- Tubulin  SOM.MK.I.BPM1.1.FTM.3.HCB.0035, SOM.MK.I.BPM1.1.FTM.3.HCB.0036, SOM.MK.I.BPM1.1.FTM.3.HCB.0038, Microtubules - Centriole and centrosome SOM.MK.I.BPM1.1.FTM.3.HCB.0039 Centriole Centrosome 9 sets of three (triplets) microtubules Two centrioles at 90° angle forms a arranged in a circular fashion centrosome Forms the core of the MTOC BPM1 | FTM| Lecture 1 | Histology of the Cytoskeleton of the Cell Connected to each other by microtubule Creates the spindle during mitosis adherence proteins (MAP) Provide basal bodies necessary for assembly of cilia and flagella centriole attached to cell membrane  SOM.MK.I.BPM1.1.FTM.3.HCB.0035, SOM.MK.I.BPM1.1.FTM.3.HCB.0036 Microtubules - Electron micrograph x30,000 magnification BPM1 | FTM| Lecture 1 | Histology of the Cytoskeleton of the Cell Centrioles (C) Nucleus (N) Microtubules (MT) Rough endoplasmic reticulum (rER) Golgi (G) Mitochondria M  SOM.MK.I.BPM1.1.FTM.3.HCB.0040, SOM.MK.I.BPM1.1.FTM.3.HCB.0041, Microtubules - Cilia & Flagella SOM.MK.I.BPM1.1.FTM.3.HCB.0037 Cilia Highly specialized motile apical specializations Hairlike structures responsible for active of cells movement of particles along the surface Consist of a core (axoneme) – found on most epithelium 9 sets of two (doublets) arranged circularly Movement is rhythmic – active stroke in around 2 the direction of movement and slightly centrally placed microtubules (9+2 less powerful recovery stroke back to BPM1 | FTM| Lecture 1 | Histology of the Cytoskeleton of the Cell arrangement) starting position Doublets are attached to each other by a pair of Dynein arms (motor proteins) Anchored to the cell via basal body Movement produced by the bending of the axoneme Flagella Long motile tails that move the entire cell – sperm cell  SOM.MK.I.BPM1.1.FTM.3.HCB.0040, SOM.MK.I.BPM1.1.FTM.3.HCB.0041 Microtubules - Primary Cilia Long non-motile, microtubule-based, antennae-like structure 9 sets of two (doublets) arranged circularly (9+0 arrangement) Emanates from almost all cells BPM1 | FTM| Lecture 1 | Histology of the Cytoskeleton of the Cell Anchored to cell via the basal body Functions as sensory antennae Photoreceptors Outer segment of rods, in the eye Chemoreceptors Odor detection of olfactory neurons Mechanoreceptors Epithelial cells monitors the flow of fluid through the kidney tubules  SOM.MK.I.BPM1.1.FTM.3.HCB.0044, SOM.MK.I.BPM1.1.FTM.3.HCB.0045 Microtubules – intracellular movement Vesicles, organelles and microtubules need to move within the cytoplasm to perform their function This is done with the aid of microtubules and motor proteins Dynein and Kinesin ATP dependent BPM1 | FTM| Lecture 1 | Histology of the Cytoskeleton of the Cell Kinesin Family (3 um/sec) Dynein Family (14 um/sec) Move in the (- ve) direction along Move in the (+ ve) direction along microtubules (Retrograde) microtubules (Anterograde) Largest & fastest of the known molecular ~ 40 distinct kinesins in humans motors  SOM.MK.I.BPM1.1.FTM.3.HCB.0030, SOM.MK.I.BPM1.1.FTM.3.HCB.0031, SOM.MK.I.BPM1.1.FTM.3.HCB.0032 Intermediate Filaments No charge at the ends = Non-polar α-helical rod-like protein subunits Coil together forming rope-like units (8-12 nm diameter) Arranged in a staggered way to increase BPM1 | FTM| Lecture 1 | Histology of the Cytoskeleton of the Cell stability and strength Assembled with the help of linking proteins = No energy required Provide structural support Essential for integrity of cell-cell & cell-ECM junctions 6 types based on their location, structurally similar but their amino- and carboxy-terminal regions are unique to each type E.g. Keratin in skin cells  SOM.MK.I.BPM1.1.FTM.3.HCB.0030, SOM.MK.I.BPM1.1.FTM.3.HCB.0031, SOM.MK.I.BPM1.1.FTM.3.HCB.0032 Intermediate Filaments – types and examples Type Names Functions Examples of where they are found Epithelial cells Acidic (I) and basic Form complex network from nucleus to I & II The major component in skin cells and (II) keratins plasma membrane in epithelial cells hair Muscle cell integrity BPM1 | FTM| Lecture 1 | Histology of the Cytoskeleton of the Cell Desmin III Support and structure Mesenchymal cells, fibroblast, endothelial cells, macrophages, Vimentin melanocytes, Schwann cells, and lymphocytes Synemin – forms part of focal adhesions Neurofilaments, Protect from mechanical stress and maintain IV Syncoilin – skeletal and cardiac muscle, synemin, syncoilin structural integrity in various cell types muscle integrity and force transduction Nuclear lamina V Structural role in the nucleus of all cells Nucleus of every cell in the body (lamins) Expressed mainly in the nerve cells and is Angiogenesis and neuronal progenitor VI Nestin implicated in their growth cell marker  Intermediate Filaments – Clinical correlates Special stains can be used to investigate disorders Certain cancers or connective tissue disfunctions can be identified staining for intermediate BPM1 | FTM| Lecture 1 | Histology of the Cytoskeleton of the Cell filaments Useful to identify the origin of secondary tumors Klatt Edward C. MD, Front Matter, Robbins and Cotran Atlas of Pathology (Fourth Edition), edited by Klatt Edward C. MD, 2021, Pages iii-iii, ISBN 978-0-323-64018-3, http://dx.doi.org/10.1016/B978-0- 323-64018-3.01001-2. (https://www.clinicalkey.com/student/content/book/3-s2.0- B9780323640183010012)  SOM.MK.I.BPM1.1.FTM.3.HCB.0030, SOM.MK.I.BPM1.1.FTM.3.HCB.0031, SOM.MK.I.BPM1.1.FTM.3.HCB.0032 Microfilaments (Actin Filaments ) Consist of round proteins = actin molecules Free actin molecules in the cytoplasm - G-actin Polymerized actin in a filament - F-actin May exist as single filaments (7 - 8 nm diameter), in BPM1 | FTM| Lecture 1 | Histology of the Cytoskeleton of the Cell bundles, or in networks Found in most cells Helps to establish a cytoplasmic protein framework Have +ve and –ve charged ends = polar Nucleation site - 3 G-actin molecules each with a bound ATP Requires ATP for polymerization  SOM.MK.I.BPM1.1.FTM.3.HCB.0030, SOM.MK.I.BPM1.1.FTM.3.HCB.0031, SOM.MK.I.BPM1.1.FTM.3.HCB.0032 Microfilaments (Actin Filaments ) – Functions Anchorage and movement of membrane proteins Terminal web Provides frameworks for the cell, attachment for microvilli and basal bodies BPM1 | FTM| Lecture 1 | Histology of the Cytoskeleton of the Cell Also found on lateral surface where cell to cell adhesions are Structural core of microvilli & stereocilia Extension of cell processes (phagocytosis and cell movement) Cell motility - Locomotion without flagella Controls the viscosity of the cytosol Aggregation of actin increases the viscosity while dispersion decreases it  SOM.MK.I.BPM1.1.FTM.3.HCB.0041 Microfilaments – Microvilli and stereocilia Cytoplasmic extensions on the apical surface of some epithelium that increase the surface area for absorption Non-motile Consist of a core of 25-30 actin filaments anchored to the terminal web BPM1 | FTM| Lecture 1 | Histology of the Cytoskeleton of the Cell Microvilli Stereocilia Cylindrical, membrane-bound cytoplasmic Unusually long microvilli - Up to 120 µm in projections - 1-3 µm in length length Limited distribution (Male reproductive system and ear)  SOM.MK.I.BPM1.1.FTM.3.HCB.0041, Comparison between microvilli and cilia microvilli cilia Actin core BPM1 | FTM| Lecture 1 | Histology of the Cytoskeleton of the Cell Terminal web Basal bodies (BB) Axoneme (Ax), (9 + 2 microtubular arrangement)  SOM.MK.I.BPM1.1.FTM.3.HCB.0043 Actin motor proteins - Myosin Also referred to as thick filaments Have a round head domain that interacts with F-actin and a tail containing an ATP-binding site BPM1 | FTM| Lecture 1 | Histology of the Cytoskeleton of the Cell Myosin tail can bind to cellular structures and pull them along the actin filament It helps to stiffen and prevent deformation of the plasma membrane Responsible for closure of the gaps in wounds Responsible for formation of the “pinch” during cell division Plays an active role in skeletal muscle contraction  SOM.MK.I.BPM1.1.FTM.3.HCB.0046, SOM.MK.I.BPM1.1.FTM.3.HCB.0047, SOM.MK.I.BPM1.1.FTM.3.HCB.0048 Microfilaments – Cell movement Signaling molecules bind to surface receptors activates second messengers induces actin polymerization toward the signal - Chemotaxis Actin web undergoes treadmilling BPM1 | FTM| Lecture 1 | Histology of the Cytoskeleton of the Cell Assembling toward the signal The polymerization produces plasma membrane protrusions Filopodia Finger-like projections Lamellipodia - fibroblasts Sheet-like structures Pseudopodia – white blood cells 3 dimensional projections Myosin accumulates at the other end of the cell Myosin-actin interaction allows for complete movement of the cell  SOM.MK.I.BPM1.1.FTM.3.HCB.0033, SOM.MK.I.BPM1.1.FTM.3.HCB.0034 Cytoskeleton – clinical correlates Some chemicals and poisons can impair the function of the cytoskeletal components Both are harmful under normal circumstances but some can be used to alleviate inflammatory conditions or downregulate excessive cell division while others cause fatal changes Microtubule poisons Actin Toxins Colchicine Phalloidin (toxin found in Amanita BPM1 | FTM| Lecture 1 | Histology of the Cytoskeleton of the Cell Treatment of gout phalloides) Binds to unpolymerized tubulin molecules Binds F-actin more tightly and G-actin Preventing polymerization Promotes excessive polymerization and inhibits depolymerization Prevents release of inflammatory initiators Inhibits cell movement Vinblastine and Vincristine Cytochalasins Inhibit the formation of mitotic spindle Block polymerization of actin Inhibits uncontrolled cell division Can be used to inhibit cell movement, Taxol® (Paclitaxel) division & induce programmed cell death Stabilizes and prevents microtubule disassembly Arrests dividing cells in mitosis Amanita phalloides -F. Stevens “death caps” or “angels of death”  Cell Inclusions - Mechanisms 1 Cytoplasmic or nuclear structures formed from metabolic products of the cell Normal cell inclusions occur in most cells Abnormal cell inclusions is a manifestation of metabolic derangements 2 1. 1 Inadequate removal of a normal substance BPM1 | FTM| Lecture 1 | Histology of the Cytoskeleton of the Cell secondary to defects in packaging and transport fatty change (steatosis) in the liver 2. 2 Accumulation of an endogenous substance genetic or acquired defects in its folding, packaging, transport, or secretion, as with certain mutated forms of α 1 -antitrypsin 3 3. 3 Failure to degrade a metabolite inherited enzyme deficiencies, typically lysosomal enzymes. lysosomal storage diseases 4. 4 Deposition and accumulation of an abnormal exogenous substance cell has neither the enzymatic machinery to degrade the substance nor the 4 ability to transport it to other sites carbon or silica particle accumulation  SOM.MK.I.BPM1.1.FTM.3.HCB.0061 Cell Inclusions - normal Functional Byproducts from metabolism Glycogen (Storage form of Lipofuscin (Brownish-gold pigment) glucose) Accumulation of oxidized lipids, phospholipids, Non-membrane-bound, TEM metals and other organic molecules as result of BPM1 | FTM| Lecture 1 | Histology of the Cytoskeleton of the Cell dense bodies lysosomal digestion Accumulates over years “Wear & tear” pigment Catabolism releases glucose for Melanin energy Dark brown/brown/reddish pigment produced by Lipids (Energy store and source of the oxidation of tyrosine short carbon chains for membrane Melanocytes in the skin & responsible for color of synthesis) skin/hair pigmentation Non-membrane bound, TEM Also produced by certain neurons of the brain dense, Fat droplets Hemosiderin Spherical droplets of triglyceride Iron-storage complex in cytoplasm Due to phagocytosis of red blood cells Liquid at body temperature Mostly found in spleen  SOM.MK.I.BPM1.1.FTM.3.HCB.0061 Inclusions Melanin Glycogen Lipofuscin BPM1 | FTM| Lecture 1 | Histology of the Cytoskeleton of the Cell Hemosiderin Lipid