EXAM II Theisen Flashcards
What percentage of the genome is encoded in our DNA?
Around 1.5%
Mitochondria undergo fusion and fission depending on environmental conditions. Which protein is important during fission, which results in two separate mito?
Dynamin-1
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
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
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
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)
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
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
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
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.
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
What are some basic functions of the cytoskeleton?
Changes cell shape
Moves the cell
Supports plasma membrane
Muscle cell contraction
List the 3 types of cytoskeleton proteins
Microtubules
Actin filaments
Intermediate filaments
Function of microtubules
Determines the positions of membrane-enclosed organelles and direct intracellular transport
Makes up centrioles and mitotic spindle
Cilia and flagella
Function of actin filaments
Determines the shape of cell’s surface; whole-cell locomotion, secretion, endocytosis
Function of intermediate filament
Mechanical strength
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
- Filopodia - via migrating fibroblasts
- Lamellipodia - via epithelial cells, fibroblasts, neurons
- Pseudopodia - via ameobae & neutrophils
What are the 3 distinctive activities that occur during cell crawling? PAR
- Polarization & protrusion - actin rich structures pushed out at front of cell
- Adhesion and traction - adhere to ECM or adjacent cells via TM receptors
- 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
- Anchoring - adherins (actin), desmosomes & hemidesmosomes (intermediate)
- Occluding - tight junctions
- Channel-forming - gap junctions
- Signal relating
State 3 features of tight junctions
- Forms a seal/barrier between cells
- Forms a fence between membrane domains - limits lateral diffusion of lipids/proteins b/w apical/basolateral domains
- 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
- Par
- Scribbles - cytoplasmic
- Crumbs - apical membrane determinant
What are the two main classes of extracellular macromolecules that the lamina consists of?
- GAGs
2. Fibrous protein
What are the 4 common glycoproteins that laminin contains?
- Type IV collagen
- Laminin - primary organizer of the sheet structure; creates heterophilic contacts for diff proteins
- Nidogen
- 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
- Fibroblastic cells - bipolar/multipolar w/ elongated shapes, grow attached to a substrate
- Epithelial-like cell - polygonal, grows attached to a substrate in discrete patches
- 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
