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Histo Cytoskeleton
Cytoskeleton Review
| Question | Answer |
|---|---|
| Name the 5 classes of IFs | I and II - Acid+Neutral/Base keratin (epidermis, epithelia). III-Desmin (muscle), vimentin(mesenchyme, endothelia,fibroblasts), GFAP (glial); IV-Neurofilament; V-Nuclear Lamins |
| What is the structure of an IF? | Conserved central rod domain (46-48nm) of 4 a-helical segments separated by non helical linkers. Helices are heptad repeats. N-term and C-term variable regions. |
| Describe the IF assembly. | Two subunits form a coiled-coiled dimer (Hetero/Homo). Two dimers form staggered anti parallel tetramer. Final IF contains 8 tetramers. |
| What marks the promotion of IF disassembly? | Phosphorylation of N-term |
| What are 4 functions of N-term and C-term ends of IF? | -Mod assembly -Project from backbone -Determine spacing between IFs -Mediate interactions between IFs and IFAP!!! (also moded by phosphorylation) |
| True or false, keratins are obligate homodimers. | False. Obligate heterodimers |
| True or False, keratin expression patterns can be used to track the source of cancer cells. | True. Cells express multiple arrays of keratin genes (8H;20S), depending on the tissue of residence. |
| IF mutations are associated with EBS. What is EBS? | Epidermolysis Bullosa Simplex. It's a blistering disease caused by mutations in K5 and K14 genes of epidermal cells. IFAP mutations can also cause EBS. Plecktin mutations can also cause EBS. |
| Class III IFs can form _____- or ______ -dimers with each other, but not with keratins. | Homo and hetero |
| Desmins are associated with what structural characteristics in muscle. | Z-discs, intercalated disks, and dense bodies. |
| Defects in Desmin may lead to ________ | Protein aggregates associated with cardio- and skeletal- myopathies. |
| Defects in vimentin may cause defects in what function? | Wound healing. |
| Vimentin is the least widely distributed IF. T or F. | F. It's found in all sorts of cells of developing muscle. |
| What is asterogliosis? | The increased expression of GFAP IFs following CNS injury. |
| GFAP IF function to support ___________ of the CNS and ___________ of the periphery. | Astrocytes; Schwann cells |
| Mutations in GFAP that result in its dysfunction lead to _______________. | Alexander's disease |
| Neurofilament core is made of ________-dimers of NF-_ and an outer surface of ______-dimers of NF-_,NF-H, and NF-_. | Homo; L; Hetero; M; L |
| Variable C-terms of NF-H and NF-M have what functions? | -Cross-link adjacent NFs -Interact with IFAPs |
| The actin network determines the diameter of an Axon. T or F. | F. The NF network does. |
| Abnormal aggregates of NF may cause numerous diseases: | ALS (amyotrophic lateral sclerosis, SMA (spinal muscular atropy) |
| What is the significance of IFAP and what is the main family will have discussed? | Plakin family: Desmoplakin, BPAG1; Plectin. They function in linking IFs with cell junctions. |
| The general structure of plakins, what is it? | central alpha helical coiled coiled domain, a C-term domain that interacts with IFs and an N-term domain that interacts with other proteins. |
| Where can Desmoplakin be found? What diseases are associated with its dysfunction? | In muscle and epithelial desmosomes linking IFs to cadherins. Stiate palmerplanter keratoderma (SPPK), blistering of the palms and soles. |
| Where can BPAG1 be found? What diseases are associated with its dysfunction? | Hemidesmosomes, along with plectins, link IF with collagen XVII or integrins. Associated with pemphigous, an autoimmune disease leading to skin blistering. |
| BPAG1 has a neuroisoform generated via alternative splicing to allow actin cross linking with IF in the axonal cortex. T or F? | T. |
| Plecktin is broadly expressed and cross links IFs to Junctions, Actin, and Microtubles. T or F? | T |
| Nuclear Lamins A,B, and C comprise the nuclear lamina. Which ones are non-essential? | A and C; they are tissue specific |
| Why do NL have longer core domains than other IF? | They contain a NLS. |
| Nuclear lamina breakdown during cell division occurs by what sort of chemical reaction? | Phosphorylation. Dephosporylation reconstitutes the lamina. |
| Although nonessential, mutations in lamins A/C can cause disease. What kind of diseases are associated with lamins A/C | EDMD; dilated cardiomyopathy; lipodystophy; or Hutchingson-gilford progeria. |
| What cytoskeletal proteins are associated with defects in the neuromuscular system? | NF (SMA); NL (EDMD); Plecktins (MD); Desmin (myopathies) |
| Which cytoskeleton is the largest, most rigid, major architectural strut of cell, and hollow tube of 25nm diameter? | Mircotubule |
| Microtubules are composed of a ___________ of alpha and beta tubulin. Each dimer has __ GTP bound to it. | Heterodimer; 2 |
| Cancer drugs: Taxol Vinblastine Cholchicine | Increase MT assembly; Decrease MT assembly; Decrease MT assembly |
| Microtubules are composed of __ (number) ____________ | 13; protofilaments |
| Dynamic instability results from: | The catching up of GTP hydrolysis to + end polymerization. This causes the stable tubulin-GTP can to turn into an unstable tubulin-GDP cap. |
| T or F; post-translational modifications of MT cause changes that are well known. | False, these modifications are not well known, but acetylation and glutaminylation are thought to increase polymer stability. |
| What composes the MTOC? | gamma tubulin and gamma-tubulin ring complex (gamma-TuRC) |
| MTOC found at the base of cilium or flagellum are called __________. | Basal bodies or centriole |
| An interphase cell has a MTOC called _______. | Centrosome |
| MAP-2,1B and tau are all: | MT stabilizing and cross-linking MAPs of the nervous system. MAP-2 is only found in the cell body and dendrites. MAP-1B and tau are only found in axon and appear to be partially redundant. |
| Hyperphosphorylation of tau are seen in.... | Several neurodegenerative diseases including alzheimer's, picks disease, PSP, FTDP-17 |
| FTDP-17 has been thought to be caused by _________ mutations in tau that lead to tau filament formation or by ___________ leading to the expression of a tau isoform that prefers to aggregate. | Missense; alternative splicing |
| Pathogenesis of tau is the result of.... | Normal axonal transport of by motors associated with tau |
| A structure composed of 9 mt doublets and around 1 mt doublet. | Axoneme |
| Disease associated with malfunction of cilia | Primary cilliary dyskinesia; PCD |
| PCD families present with three main symptoms | Male sterility; respiratory illness; 50% incidence of situs inversus |
| Nexin linkages | The linkages between the inner and outer MT doublets that create the restrained MT mobility and resulting in the characteristic flagellar or cilial movements |
| What are the three domains of Dynein? | HC-ATP and MT binding sites; the motor domain. Intermediate C-facilitate complex assembly and attachment to cargo. LC-regulate activity and also interact with cargo. |
| Dyneins are _____ directed and Kinesins are ______ directed. | Minus; Plus |
| Kinesin _________ domain are conserved. Thus, MT and ATP binding sites are conserved. | Motor (may be on N, C, or intermediate parts of the polypeptide) |
| What is the significance of KIF1Bb? What disease is it associated with? | This motor is important in synaptic vesicle transport. Charcot-Marie-Tooth Disease Type 2A - muscle weakness and atrophy of the distal muscle, decreased deep tendon reflexes, and mild sensory loss. |
| KIF3 gene mutations can result in ____________ or ____________ defects. | Embryonic death, left right |
| Mech. for KIF3 left right defect is..... | KIF3 motor is need in cilia/flagelum assembly. They are involved in the anterograde intraflagellar transport for axoneme precursors. |
| Symptoms associated with cilliopathies | PKD; Retinitis pigmentosa; Polydactyly and limb defects; obesity |
| Dynein family is composed of 16 genes; __ axonemal and __ cytoplasmic | 14;2 |
| Dynein ____ is broadly expressed in cell types and ____ is enriched in ciliated tissues where it functions as the retrograde moto for intraflagellar transport. | DHC1; DHC2 |
| LIS1 gene mutation can lead to __________(smooth brain) | Lissencephaly |
| Lissencephaly | Dissorganization of cortical neurons resulting from failure in neuronal migration during brain development. |
| LIS1 protein | Found to play a role in an enzyme that inactivated platlet activating factor. It also interacts with cytoplasmic dynein and affects nuclear migration and mitosis. |
| Doublecortin (DCX) | 2nd lissencephaly locus, which also encodes a MTAP. |
Created by:
jgenere
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