the cell - american academy of osteopathy

From Molecules to Tissue

The body as a continuous interwoven matrix linking macro-organism to subcellular

structureF.H. Willard, Ph.D.

Department of AnatomyUniversity of New England

College of Osteopathic MedicineBiddeford, Maine

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Mechanotransduction

Can an external mechanical stimulus alter gene expression in a cell?

If so, how?

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Anatomical Summary

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The Cell

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The Nucleus

D. Fawcett. The Cell, Philadelphia:W.B. Saunders

Co., 1981.

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Squamous Cells

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Cuboidal Cells

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ColumnarCells

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Stratified Squamous

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Cell Shape Influences Nuclear Shape

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Nucleus

M. H. Ross and W. Pawlina. Histology, A text and atlas with correlated cell and molicular biology, Philadelphia:Lippincott, Williams & Wilkins, 2011.

EnvelopeMatrixPores

Nucleoplasm

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Nuclear Pores

M. H. Ross and W. Pawlina. Histology, A text and atlas with correlated cell and molecular biology, Philadelphia:Lippincott, Williams & Wilkins, 2011.

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The Nuclear Matrix


Laminin

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LINC

• Linker of Nucleoskeleton and Cytoskeleton

• Involves several complexes of peptides:

• Nesprin

• Lamin

• Sun

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Chromatin and Chromosome Structure

HistonesNucleosome

Chromatin fibrilLoop domains

Chromosome fibersChromosome

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Anatomical Summary

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Mitosis

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V. Kumar, A. K. Abbas, and N. Fausto. Robbins and Cotran Pathological Basis of Disease, Philadelphia:W.B. Saunders

Co., 2005.

Cell CycleRegulation

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Co., 2005.


TFGβ

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Co., 2005.


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Co., 2005.


cMyC +

estrogen +

Wnt +Shh +

EGF +

TGF-B -

cKit +Wnt +

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Cytoplasm

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Random distributionor

Organized network

Cytosol vs. Cytoskeleton

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Rough Endoplasmic Reticulum

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Protein Synthesis

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A. J. Macario and de Macario Conway. Sick chaperones, cellular stress, and disease. N Engl J Med 353 (14):1489-1501, 2005.

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The Proteasome

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Endoplasmic Reticulum and Pathology

Deposition Diseases

• Demyelination

–Charcot-Marie-Tooth syndrome

• Degeneration

–Alzheimer’s disease

Ubiquitin-Proteosome PathwaySunday, May 5, 13

CytoskeletonMicrotubules - 20-25 nm

in diameter

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CytoskeletonIntermediate filaments -

8-10 nm in diameter

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CytoskeletonThin filaments - 6-8 nm

in diameter

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Thin Filaments

F-Actin membrane

attachments to the ECM

SpectrinDystrophin

Sol-Gel Model

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Cell Membrane

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Integral Membrane Proteins


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Cell Signaling Pathways

G-Proteins

1) Receptor conformational change2) GDP exchanged for GTP3) Dissociation of subunits4) Activation of adenylate cyclase5) ATP converted to cAMP + PPi6) GTPase (GAP) hydrolyzes GTP

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Receptor Mechanisms

D. Julius and A. I. Basbaum. Molecular mechanisms of nociception. Nature 413 (6852):203-210, 2001.

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Cell Signaling PathwaysRas, Rho, ROCK

Messenger-dependent transmission

vs.Distortion-dependent

tranmission

GAP - GTPase Activating Protein

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MAPK Pathway

Gortazar AR, Martin-Millan M, Bravo B, Plotkin LI, Bellido T. 2013. Crosstalk between caveolin-1/ERKs and beta-catenin survival pathways in osteocyte

mechanotransduction. J Biol Chem.

Mechanical stress activates the MAPK (ERK) pathway preventing apoptosis in cultured osteocytes

Mitogen-activated Protein Kinase

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Transforming Growth Factor - beta Pathway

DAXX Pathway SMAD Pathway

TGF-β, acting through its signaling pathway, stops the cell cycle at the G1 stage to stop proliferation, induce differentiation, or promote apoptosis.

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c-KIT or CD117Receptor Tyrosine Kinase

AKT = Protein kinase BSCF = Stem Cell Factor

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Wnt/CateninSignaling

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Cell Membrane


Polarity

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Epithelial Cell Polarity

Occluding junctionsAnchoring junctions

Communicating junctionsM. H. Ross and W. Pawlina. Histology, A text and atlas with correlated cell and molecular biology, Philadelphia:Lippincott, Williams & Wilkins, 2011.

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Occluding Junctions


Zonula Occludens

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Claudin(To Close)

PDZ zones

Occluding Junctions

Zonula Occludens

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Anchoring Junctions

Cell-to-Cell

Zonula adherens

Macula adherens

Cell Adhesion Molecules

Actin-binding

Intermediate filament-binding

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CDH-1 Gene

Cadherin-1or

E-cadherin

E-cadherin Endothelia

N-cadherin Neurons

P-cadherin Placental

Cadherin-12 Neurons

Desmoglein Epidermis

Desmocollin Epidermis

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Anchoring Junctions

Cell-to-ECM

HemidesmosomeInvolve Intermediate filaments

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Anchoring Junctions

Cell-to-Matrix

Focal AdhesionInvolve Actin filaments

“Tent-Pegs”

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Focal Adhesion Gartner LP, Hiatt JL. 2000. Color Atlas of Histology. 3rd ed. Philadelphia: Lippincott Williams & Williams.

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Focal Adhesions

• Involve actin filaments

• Mechanosensitive

• Sensitive to cell shape and force in ECM

• ECM side: integrins, fibronectin, laminin, vitronectin

• Cell side: talin, actinin, filamin, vinculin, paxillin, focal adhesion kinase

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Communicating Junctions

Cell-to-Cell

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Integrin“Adhesome”

B. Geiger, J. P. Spatz, and A. D. Bershadsky. Environmental

sensing through focal adhesions. Nat.Rev.Mol.Cell Biol. 10 (1):

21-33, 2009.

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Cell Junctions

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Human ThickSkin

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Full ThicknessHuman Skin

CulturedHuman Skin

Cells

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Finger Pad

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Attachment of the Epidermis to the Dermis

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Extracellular Matrix

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Dense Irregular Connective Tissue

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Extracellular Matrix

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Collagen

• 25 Known types

• 1 Most connective tissue

• II Cartilage

• III Reticular fibers

• IV Basal lamina

• X Bone mineral matrix


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CollagenTypes

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Elastic Fibers


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Elastic Connective Tissue

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Reticular Fibers

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Basement Membrane

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Form & Function

LCT

DCT

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Fibroblasts

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ConnectiveTissueCells

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Fibroblasts

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Myofibroblasts

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Endothelial Cells

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Mesothelial Cell

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Adipocytes

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Chondrocytes

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Osteocytes

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ConnectiveTissueCells

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ECM

• Hyaluronic acid

• Glycosoaminoglycans

• Proteoglycans

• Multiadhesive glycoproteins

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ECM Structure


GAGsProteoglycans

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M. H. Ross and W. Pawlina. Histology, A text and atlas

with correlated cell and molecular biology,

Philadelphia:Lippincott, Williams & Wilkins, 2011.

Glycosoaminoglycans

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ProteoglycanMonomers

M. H. Ross and W. Pawlina. Histology, A text and atlas with correlated cell and molecular biology,

Philadelphia:Lippincott, Williams & Wilkins, 2011.

Cartilage

Connectivetissues

Fibroblastmembranes

Connectivetissues

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Multiadhesive Glycoproteins:

FibronectinLamininTenascin

OsteopontinEntactin/Nidogn

Anchoring Junctions

Cell-to-ECM

“The Adhesome”Binding sites; Interact with cell-surface receptors

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Life in a Prestressed Environment

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Cellular Tensegrity

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A. Mammoto, T. Mammoto, and D. E. Ingber. Mechanosensitive mechanisms in transcriptional regulation. J.Cell Sci. 125 (Pt 13):3061-3073, 2012.

Mechanotransduction Pathways Responding to Mechanical Stress

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Force Transduction from Skin to Skeleton

The Cellular and Molecular Organization of the Body

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Cells & TissueFrom Skin to

Bone

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Fibroblasts

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Tissue Marophage

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Medialepicondyle

Semimembranosus tendon

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Tendon

Paratenon

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FetalExtremity

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FetalSkeletalMuscle

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SkeletalMuscle

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Bone&

Periosteum

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Bone

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Osteocytes

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Summary

The integrated multi-dimensional network, involving cells and extracellular matrix, that exists from the external surface into the deepest of the internal structures.

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Force

Anchoringjunction

Cytoskeleton

Signal transductionpathway

Change in cellphysiology

Cell-MatrixInteractions

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Mechanical Force

Anchoringjunction

Cytoskeleton

Signal transductionpathway

Change in cellphysiology

Cell-MatrixInteractions

Change in geneexpression

Nucleus

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Mechanotransduction and Cell Metabolism

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Mechanotransduction and Cell Metabolism

D. E. Ingber. Tensegrity: The architectural basis of cellular mechanotransduction. Ann.Rev.Physiol. 59:575-599, 1997.

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Anatomical Summary

Prestressed StateSunday, May 5, 13

Cells need to feel the force

D. E. Jaalouk and J. Lammerding. Mechanotransduction gone awry. Nat.Rev.Mol.Cell Biol. 10 (1):63-73, 2009.

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Mechanotransduction

• Mechanical force acting on a cell membrane

• Opening of mechanosensitive pores

• Distortion of mechanosensitive proteins

• Signal transduction into the cell & nucleus

• Generation of a cellular response

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Mechanotransduction and Gene Expression

N. Wang, J. D. Tytell, and D. E. Ingber. Mechanotransduction at a distance: mechanically coupling the extracellular matrix with the nucleus. Nat.Rev.Mol.Cell Biol. 10 (1):75-82, 2009.

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Summary

• All cells of the body are interconnected in a “multiscale” matrix

• The matrix exists in a “prestressed” state

• All cells of the body can sense position and movement through this matix

• All cells of the body need this sense to survive within this matrix

• Extracellular fluids are important in maintaining the prestressed state

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the cell - american academy of osteopathy

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