Unit 3 - Cell Structure, Adhesion & Replication

UTIs are caused by

UPEC

UPEC Infection Process

1. UPEC adheres with pili

2. Takes and replicates

3. Burst cell to repeat cycle

Pili

Lectin proteins that interact with mannose-glycoprotein in epithelial

Lectins

Made of FimA, D, H and G

FimH

Adhesive on the tip, and necessary for assembly of type 1 fimbriae

FimF and G

Attachment proteins

FimA

Creates length

FimD

Anchor

Mannose-Containing Glycoproteins

Oligosaccharide units

Proanthocyanides

Polyphenol molecule in cranberries that decrease UPEC adherance

Inhibitor Cocktail

Combination of inhibitors that target many different bacteria adhesion molecule

Inner Cell Mass

Forms early embryo

Embryo Layers

Endoderm, Ectoderm, Mesoderm

HV Wilson Experiment

Separate 2 sponge cells with a mesh, then mixed them together which they eventually clump in their own species naturally

Johannes Holtfreder

Took cells from eggs ectodermal and mesodermal to separate them, but the cell aggregated by type

Cell Adhesion Molecules (CAMs)

Transmembrane proteins that help with clumping of like cells

Junctions

Formed after aggregation stabilize cell interactions and facilitate communications between cells

Epithelial Sheets

Form inner lining of digestive system and outer skin

Basal Surface

Anchored to extracellular structures that give structure to sheets of cells, includes basal lamina, basement membrane

Hemidesmosomes

Anchors cells to extracellular matrix on basal region

Adhesion Complexes

Connects lateral surfaces

Types of Adhesion Complexes

• Tight junctions

• Adherence junctions

• Gap junctions

• Desmosomes

Tight Junctions (Zonula Occludens)

Below the apical surface of occludin and claudin to form continous seals to stop diffusion between apical and basolateral

Occludin and Clotin

Closely arrange between neighbouring cells

Gap Junctions

1-5-2 nm width that directly links cytosol of two cells, allowing for metabolic integration through ions (cAMP, Ca)

Hexagonal Connexin Hemichannel

6 individual nexin protein subunits

Hemichannels

Link up with other cell’s hemichannels to allow for rapid coordination of cardiac and uterine muscle contractions

Plasmodesmata

Like gap junctions in plant cells for phloem structure

Phloem

System of elongated tubes from linear arrays of connected cells, carrying nutrients like products of photosynthesis, from leaves to plants

Sieve Tube Elements

Phloem cells connected by menlarged plasmodesmata that form the sieve tube plate

Companion Cells

Associated with development and function of sieve tube elements by giving ATP, proteins and connects to the phloem cells by plasmodesmata

Communication through Plasmodesmata happens through

Transcription factors, gene transcripts, sRNAs

Viral Pathogens exploit

Gap junctions to facilitate cellular spread

Anchoring Junctions

• Hemidesmosomes

• Adherens junctions

• Desmosomes

All associated with actin filaments

Desmosomes

Links two cells together

Adherens Junctions

Indirectly connect actin cytoskeleton between neighbour cells

Homophilic Interactions

Association of similar cells

Heterophilic Interactions

Connects different cells together

Families of CAMs

• Cadherins (IG superfamily)

• Integrins

• Selectins

Cadherins

Ca dependent CAMs that mediate homophilic interactions

E-Cadherin (Epithelial Cadherin)

Mediates Ca dependent adhesion of epithelial cells

N-Cadherin

Neural cadherin

P-Cadherin

Placental cadherin

Adhesion controlled by

Transmembrane coherence and cytosolic co-factors

Catenin

Anchors cadherins to actin

Endothelial Cells

Specialized epithelial cells that form the walls of the blood vessels

Extravasation

Cells/fluids move from blood vessel/capillary into surrounding tissue

Types of Leukocytes

• Granulocytes

• Monocytes

• Lymphocytes

Grandulocytes

Targets pathogens, include neutrophils, eosinphils, basophils

Neutrophils

Most numerous, primarily targets bacterial infections and trauma

Moncytes

Differentiates into macrophages

Natural Killer Cells (NK)

Lyse virally cells and tumour cells

T and B cells

Make antibodies as part of immune response

Capture

Injury signal, mediated with cytokines and basal receptors that triggers release of selectins to appear on apical layer

P Selectins

Interacts with selectin specific glycoprotein in leukocytes, held in secretory vesicles until cytokine signal

Platelet Activating Factor (PAF)

Membrane anchored signal interacts with neutrophil’s paf receptor

PAF Receptor

Only happens when slow rolling occurs with neutrophils and interacts with PAF

PAF Binding

Initiates changes in gene expression and activation of integrin adhesion molecules on the neutrophil

Firm Adhesion

Integrin interacts with icamps that further slows movement

Integrins

Dimeric protein with propeller and alpha-beta domains that form the ligand binding domain and folded down when inactivated

Activation of Integrins

Signals for reorganization of actin cytoskeleton

Transmigration

Protease breaks down the endothelial cell adhesion, causing swelling from leaked blood and migration of neutrophils

Transendothelial Migration

Complete migration of neutrophil through the vessel wall into surrounding connective tissue

Dynamic Instability

Both polymerization and depolymerization, making the spindle self organizing

Centrosome

Made up of mother and daughter centriole and PCM

Pericentrilar Material (PCM)

Has y-Turc where microtubules nucleates and polymerizes

CDK and PLK4 Kinase

Initiates centrosome duplication in G1/S phase

M Phase CDK

Initiates centrosome splitting

Spindle Poles

2 MTOC on opposite sides

Bipolar Mitotic Spindle

Microtubule based machine that segregates duplicated chromosomes

Astral Microtubules

Links to cell cortex to anchor spindles

Polar Microtubules

Projects to the centre and overlap each other to help with pushing microtubules apart

Kinesin 1 and 2

2 ATP heads and a cargo binding subunit

Kinesin 5

Has no motor activity but helps with end diassembly

Bipolar Attachment

Chromosome attaches to spindle microtubules from each poles

Spindle Assembly Checkpoint

Forces from each kinetochore must be equal in order for anaphase to occur

Prophase

Mitotic spindle assemble, centrosomes move to opposite poles

Prometaphase

Chromosomes attach to bipolar microtubule spindles, kinetochores assemble at centromeres

Metaphse

Bipolar attachment, tension from chromosomes being pulled causes it to line up on metaphase plate

Telophase

Chromosome decondenses, mitotic spindle disassembles and endomembrane and nuclear envelope reassemble

Cytokinesis

Cell pinches from actin filament and myosin

Cyclin CDK Complexes

Heterodimer protein complexes that facilitate regulated phosphorylation

A-Cyclin

Regulates CDKs

E3 Ligase Complexes

Target specific protein for degradation in proteasome to turn off kinases or cell cycle inhibitors

Skip Cullen F box (SCF) Complexes

Releases cell from G1 and allows transition into S phase

Anaphase Promoting Complex (APC)

Has different target proteins depending on its accessory protein (CDC20 or CDH1)

APC CDC20

Regulates transition from metaphase to anaphase

APC CDH1

Regulates Exit from Mitosis

G1 Cyclin CDK

Targets phosphorylation of APC CDH1 to stop mitotic breaks, and inhibitors, and prepare S phase transcription

G1 S phase Cyclin CDK

Prepares for S and M phase by activating E2F and transcription of mitotic regulators

G1 S Phase Cyclin CDK phosphorylate

Activates DNA replication genes, and phosphorylates proteins to only fire once

M Phase Cyclin CDK Complex phosphorylates

• Chromosomal proteins

• Nuclear lamina

• Microtubule proteins

• Kinetochore proteins

• APC Complex

Phosphorylation of Condensins and Histones

Chromosomes condense

Phosphorylation of Nuclear Lamina

Breakdown envelope

Phosphorylation Microtubule Proteins

Formation of mitotic spindle and centrosome separation

Phosphorylation of Kinetochore Proteins

Chromosome spindle association

Phosphorylation of APC Complex

Cell progression

Metaphase to Anaphase Transition (MAT)

Anaphase inhibitors degrade

Mitotic Exit Network (MEN)

Mitotic cyclin degrades to exit mitosis

Mitosis Promoter Factor (MPF)

Cyclin B + CDC2 that regulates phosphorylation