Molecular Cell Biology. Intermediate Filaments Cooper

Transcription

1 Molecular Cell Biology Intermediate Filaments Cooper

2 Introduc7on Filaments 10 nm wide => intermediate Present in Metazoa / Animals i.e. not Plants or Unicellular Organisms Complex Gene Superfamily 70 in Human Genome Specific Expression at Different Times and Places

3 Intermediate Filament Biochemical Proper7es In Vitro Very stable. LiUle subunit exchange. Very strong. Filaments do not break. MT s strong but briule Ac7n weak

4 Intermediate Filament Poten7al Func7ons In Vivo Mechanical Strength of Cytoplasm Help a Layer of Epithelial Cells Resist Shear Stress - Filaments Connect to Cell- cell Junc7ons Hold Nucleus in Center of Cell

5 Intermediate Filament Structure & Assembly

6 Intermediate Filaments by EM: Filament Unraveling

7 Classes of Intermediate Filaments Class Name Cells Number of Isoforms Size (kd) Polymers I Acidic Keratin Epithelia ~ Obligate Heteropolymers II Basic Keratin Epithelia ~ One acidic + one basic III Vimentin Mesenchymal 1 53 III Desmin Muscle 1 52 Homopolymers (single III Glial Fibrillary Glia 1 51 type of subunit) or Acidic Protein (GFAP) co-polymers w/ each III Peripherin Neurons >1 58 other at varied ratios IV Neurofilament H Neurons IV Neurofilament M Neurons H & M each require IV Neurofilament L Neurons L for polymer IV Nestin Glial scars, Early neurons & muscle V Lamin A All Homopolymers or V Lamin B All Heteropolymer

8 Regula7on of IF Assembly Notoriously Stable No Nucleo7de Filaments Move LiUle Precursors Move More Disassemble Somewhat during Mitosis Phosphoryla7on by Cyclin- depen Kinase

9 Vimen7n Filaments in a Cultured Cell

10 Vimen7n All Cells in Early Development Cage Around Nucleus Interacts with Mt s Vimen7n Knockout Mouse Ini7ally normal at gross inspec7on Cultured cells have altered proper7es of uncertain significance

11 FRAP of Vimen7n vs. Kera7n in One Cell Left: Vimentin (Green) Right: Keratin (Red) 10 min time intervals

12 Dynamics of Kera7n Par7cles in Periphery 11 micrometers over 10 minutes 18 micrometers over 10 minutes

13 Dynamics of Kera7n Par7cles in Periphery 11 micrometers over 10 minutes 18 micrometers over 10 minutes

14 Dynamics of Kera7n Par7cles in Periphery 11 micrometers over 10 minutes 18 micrometers over 10 minutes

15 Desmin Expressed in Muscle Elas7c Elements to Prevent Over- stretching Connects / Aligns Z lines Knockout Mouse - Deranged Myofibril Architecture

16 Kera7ns Expressed in Epithelia Kera7n Filaments Connect to Desmosome and Hemidesmosomes Differen7a7on of Epidermis includes Produc7on of Massive Amounts of Kera7n Provides Outer Protec7on of Skin Composes Hair, Nails, Feathers, etc.

17 Density of Kera7n Filaments in Outer Epidermis Layers

18 Kera7n Muta7ons are Basis for Human Epidermal Diseases Structure/Func7on Analysis of Kera7n Assembly Point Muta7on in Terminal Domain Fails to Assemble Mutant is Dominant, even in Low Amounts, in Cultured Cells and Mice

19 Epidermolysis Bullosa Simplex Wild-type Mutant

20 Kera7ns and EBS

21 Neurons Neurofilament H, M, L Copolymer Prevent Axon Breakage Diseases with Clumps of Neurofilaments Superoxide dismutase model for ALS Clumps are secondary, not causa7ve

22 Neurofilament Transport in Axons Photobleached Zone in the Middle

23 Neurofilament Transport in Axons Photobleached Zone in the Middle

24 Lamins Square Lacce on Inner Surface of Nuclear Membrane Present in Metazoans (Animals, not Plants or unicellular organisms) Mitosis Breakdown Phosphoryla7on of A & C by Cyclin- depen Kinase B remains with Membrane Muta7ons Cause Accelerated Aging Diseases Progerias - Dominant Muta7ons

25 EM of Nuclear Lamina Nuclear Pores

26 End