EXAM II Theisen Flashcards by Erin O

What percentage of the genome is encoded in our DNA?

Around 1.5%

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Mitochondria undergo fusion and fission depending on environmental conditions. Which protein is important during fission, which results in two separate mito?

Dynamin-1

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Why are there a lot of diseases associated with mitochondria?

Mito contain no DNA repair mechanisms, which results from tRNA problems which is involved with translation

Mito holds a tRNA genes

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What are the 2 major types of responses that occur from signal transduction (cell signaling)? Which one involves proteins, which one involves gene transcription?

Fast Response = change in activity or function of enzymes or proteins, i.e cAMP

Slow Response = change in protein amount or gene expression

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What are the 3 types of cell signaling receptors that are located within the plasma membrane?

Ion-channel coupled receptors (common in nervous tissue)

GPCRs - 7-pass transmembrane proteins

Enzyme-coupled receptors - i.e. tyrosine kinase

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T/F Heterotrimeric (alpha,beta,gamma) G-proteins have intrinsic catalytic activity

False; NO intrinsic catalytic activity

3 components of receptor; EC domain, TM domain, cytosol domain (associates w/ G proteins)

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Cholera toxin modifies G protein, causing increasing cAMP activity, which subunit of the G protein does cholera modify?

Keeps G-alpha in the GTP active form indefinitely

Leads to 100-fold increase in cAMP

PKA phosphorylates the CFTR Cl- channel = water secretion

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Define desensitization of a signal

The ability to turn off or reject a signal (important for cancer)

Potentiate = to turn up
Attenuate = to turn down

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What is the role of G-protein receptor kinase in signal desensitization?

GRKs phosphorylate the receptor such that another protein (i.e. arrestin) will bind to the 3rd intracellular loop of GPCR preventing G-alpha from interacting with the third loop

The result is that the G-alpha-GDP does not get converted to G-alpha-GTP

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Which receptor creates docking sites for other proteins?

a. GPCR
b. Enzyme coupled receptors (i.e. tyrosine kinase)
c. Ion-channel coupled receptors
d. all of the above

Enzyme-coupled receptors (tyrosine kinase)

JAK-STAT Receptors
Serine/Threonine kinases, etc.

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Where is the enzymatic domain of enzyme-coupled receptor tyrosine kinase? What are other features of this receptor?

Cytoplasmic tail of the integral membrane protein

Single pass transmembrane domain

Ligand binding induces dimerization of two receptor monomers

Autophosphorylation = recruits SH2 DOMAIN of Grb2 = binds phosphotyrosine

Important for growth factors

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What are some basic functions of the cytoskeleton?

Changes cell shape
Moves the cell
Supports plasma membrane
Muscle cell contraction

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List the 3 types of cytoskeleton proteins

Microtubules

Actin filaments

Intermediate filaments

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Function of microtubules

Determines the positions of membrane-enclosed organelles and direct intracellular transport

Makes up centrioles and mitotic spindle

Cilia and flagella

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Function of actin filaments

Determines the shape of cell’s surface; whole-cell locomotion, secretion, endocytosis

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Function of intermediate filament

Mechanical strength

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Cytoskeletal filaments undergo a lag phase, growth phase, and equilibrium (steady state) phase. What is required in order for it remain in the steady phase?

Critical concentration (Cc) - the rate of addition of new subunits balances the rate of dissociation

Tubulin is a heterodimer containing alpha and beta-tubulin, what do they have binding sites for?

What binding sites are locating in the actin monomers?

GTP; the GTP in alpha-tubulin is never hydrolyzed

Longitudinal contact = alpha-beta
Lateral contact = alpha-alpha, beta-beta

Actin monomers = ATP binding sites; arranged head to tail (flexible, easily bent)

What is the rate limiting step in the formation of the cytoskeleton?

Nucleation (via gamma-tubulin)

ARP proteins, which are accessory proteins of actin filaments contains Arp2/3 complex, what allows them to bypass the rate-limiting step of filament nucleation?

When the complex binds to the activating factor which induces a conformational change; repeated rounds of branching can occur creating a highly branched web of actin filaments

Works similar to gamma-TuRC = nucleation at (-) end

While ARP2/3 complex creates branched actin filaments, formins create what type of pattern?

Straight/unbranched actin filaments

Dimeric proteins; binds (+) end (OPPOSITE from gamma-TuRC)

How is there a large pool of actin polymers always kept available when all the nucleation of actin filaments occurring in the cell? Which accessory protein is important here?

Thymosin - keeps actin monomers soluble so that they are readily available for generating filaments

When monomers are bound to thymosin, they can’t associate with actin filaments

Define catastrophe of stability, which proteins are involved

Change from growth to rapid shrinkage

Kinesin-13

XMAP215

Alpha-actinin vs. Fimbrin (cross-linking proteins)

alpha-actinin = cross-linkage, loose bundles, allowing myosin II to enter; contractile

Fimbrin = cross-linkage into tight bundles, excluding myosin II; parallel bundles

List the 3 plasma membrane protrusions

FLiP - dense core of actin filaments, no organelles 1. Filopodia - via migrating fibroblasts 2. Lamellipodia - via epithelial cells, fibroblasts, neurons 3. Pseudopodia - via ameobae & neutrophils

What are the 3 distinctive activities that occur during cell crawling? PAR

1. Polarization & protrusion - actin rich structures pushed out at front of cell 2. Adhesion and traction - adhere to ECM or adjacent cells via TM receptors 3. Retraction - adhesion disassembly at rear

What are the two main ways to connect animal cells and to provide the strength to connect?

Connective Tissue Epithelial Tissue

List the 4 types of cell-cell junctions

1. Anchoring - adherins (actin), desmosomes & hemidesmosomes (intermediate) 2. Occluding - tight junctions 3. Channel-forming - gap junctions 4. Signal relating

State 3 features of tight junctions

1. Forms a seal/barrier between cells 2. Forms a fence between membrane domains - limits lateral diffusion of lipids/proteins b/w apical/basolateral domains 3. Recruits cytoskeleton and signaling molecules at the cytoplasmic side

What are the 3 polarity proteins involved in the polarization process of the epithelial cells?

Eating a Par Sandwich 1. Par 2. Scribbles - cytoplasmic 3. Crumbs - apical membrane determinant

What are the two main classes of extracellular macromolecules that the lamina consists of?

1. GAGs | 2. Fibrous protein

What are the 4 common glycoproteins that laminin contains?

1. Type IV collagen 2. Laminin - primary organizer of the sheet structure; creates heterophilic contacts for diff proteins 3. Nidogen 4. Perlecan

Define focal adhesion = integrins!!!!!!

Prominent and durable actin-linked cell-matrix adhesions (integrins!!!!!!!!) formed when fibroblasts have sufficient time to form the strong attachment to the rigid surface Common in hemidesmosomes w/ keratin filaments attached in intracellular domain Defects = blistering

What structures interact in focal contacts?

ECM Integrins Cell cytoskeleton

What protein is prominent in focal adhesions?

FAK = focal adhesion kinase = cytoplasmic protein tyrosine kinase, recruited by talin/paxillin = MAXIMAL ACTIVATION = PHOSPHYLATION VIA SRC Related to Src and docking sites for Src-family kinases = helps regulate cell division, growth, survival

What cell type makes/secretes the ECM that's located in the ECM?

Fibroblasts!!!!!!

Basic collagen structure, which amino acids make it up?

Triple-stranded helical structure - 3 polypeptide chains Proline and glycine

What is the importance of hydroxyl groups in fibroblasts?

Create affinity = strong binding between fibers

Importance of prolyl/lsyl hydroxylases in collagen?

Provides strong binding b/w Hydrogen fibers = allows superhelix to remain tightly bound

List the 3 morphologies of common cell lines and describe their shapes

1. Fibroblastic cells - bipolar/multipolar w/ elongated shapes, grow attached to a substrate 2. Epithelial-like cell - polygonal, grows attached to a substrate in discrete patches 3. Lymphoblast-like cells - spherical, usually grown in suspension w/out attaching to a surface

List advantages and disadvantages of cultured cells lines

Advantages = no use of animals, good reproducibility b/w experiments, control of environment, can expose cultures to reagents Disadvantages = costly, must dev standardized techniques, time to learn aseptic technique, limited quantity, dedifferentiation & selection can occur and many original cellular mech can be lost