golgi vesicles and traffic

Question 1

HVC

Answer 1

• hijacks host lipid metabolism and remodels host membranes to envelope itself
• double membrane vesicles

Question 2

endomembrane system

Answer 2

• organelles are connected directly by membranes or indirectly by transfer of membrane segments

Question 3

nuclear envelope + endoplasmic reticulum

Answer 3

• lumen of perinuclear cisternae is in continuity with the RER lumen
• outer membrane is similar to the membrane of RER
• inner has a different composition
• 2 types of membrane invagination into nucleoplasm
• GFP lamin

Question 4

the endoplasmic reticulum

Answer 4

• extensive membrane network of cisternae and tubuli
• quantity of ER quickly varies upon cell activation
• smooth ER lacks ribosomes on surface: site for lipids (steroids) synthesis and detoxification
• RER: ribosomes stud the surface: site for protein synthesis: products transferred via vesicles
• ER in most eukaryotic cells sequesters Ca2+ from cytosol

Question 5

RER:how do ribosomes bind?

Answer 5

• ribosomes not a stable part: constantly being bound and released from the membrane
• ribosomes bind through a receptor called ribophorin when it begins synthesis a protein to be secreted
• protein glycosilation begins in the RER and is completed in golgi
• vesicles shuttle proteins between these two compartments

Question 6

RER hypertrophy and acinar cells

Answer 6

• a significant increase in its amount
• acinar cells of exocrine portion of pancreas are abundant in ER
• principal site of pancreatic juice production
• pancreatin and other digestive enzymes are produced in RER and stocked in secretory granules

Question 7

visualising the RER

Answer 7

• RER is basophilic
• HandE, Nissl stain, GFP labeled proteins, IF,

Question 8

smooth endoplasmic reticulum

Answer 8

• in mainly cells are scanty and often party smooth and partly rough
• prominent in cells that specialise in lipid metabolism (e.g. steroid hormone synthesis
• many other reaction occur in SER: Gierke’s disease

Question 9

hepatocytes and SER

Answer 9

• rich in SER
• principal site of production of lipoprotein particles
• SER contains enzymes that detoxify both lipid-soluble drugs and various harmful compounds produced by metabolism

Question 10

muscle cells and SER

Answer 10

• muscle fibers abundant is specialised SER: sarcoplasmic reticulum
• release and uptake of Ca2+
• Ca2+ storage in lumen is facilitated by high cc of Ca2+ binding proteins

Question 11

Von Gierke’s disease

Answer 11

• glycogen storage disease type 1
• accumulation of glycogen in cytoplasm
• clinical signs: inadequate blood glucose levels, enlargement of liver, damage to tissue from hyperuricemia, bleeding infections
• deficiency of glucose-6-phosphatase enzyme located of SER membrane impairs ability of liver to produce free glucose from glycogen

Question 12

free ribosomes

Answer 12

• in cytoplasm
• appear as 25 nm granules by TEM
• synthesise proteins that remain in cytosol
• form clusters called polyribosomes

Question 13

golgi apparatus localisation

Answer 13

-positioned near the centrosome based microtubule-organizing center
- subdivided into 3 functionally distinguished compartments
- CIS forming face: vesicles fusing facing RER : network of membranous tubules appearance
- cis cisterna, medial cisterna, trans cisterna
- Trans maturing face releasing vesicles
- two alternative models for flux through golgi complex

Question 14

golgi functions

Answer 14

• post-translatioal modifications and sorting of neo-synthesize proteins
• synthesis of polysaccharide molecules (proteoglycans, mucins) and lipids
• sorting and dispatching station for the products of RER
• most glycosylation reactions occur in golgi
• signal-mediated diversion to lysosomes
• signal-mediated diversion to secretory vesicles for regulated secretion
• constitutive secretion
• N-glycosilation starts w addition of an oligosaccharide to NH2 group of an asparagine side chain

Question 15

cells with a well-developed golgi

Answer 15

• secretory cells
• synthesizing large amount of membrane and membrane-associated proteins

Question 16

intracellular traffic

Answer 16

• multidirectional, based on vesicle trafficking
• endocytic and biosynthetic secretory pathways
• retrieval pathway: maintenance of selected components backflow

Question 17

vesicle traffic

Answer 17

• complex but not chaotic
• membrane-bound proteins facing the cytosol target vesicles to their destination

Question 18

vesicle budding

Answer 18

• coat assembly and cargo selection: specific receptor for cargo molecules
• cargo receptor and adaptin bind to clathrin
• vesicle formation: dynamin: clathrin coated vesicle
• uncoating: naked transport vesicle

Question 18

coating functions

Answer 18

• to gather proteins in specific membrane region where vesicle should bud ensuring selective cargo
• to add rigidity determining the shape and size of the vesicle

Question 18

coating proteins (COP)

Answer 18

• 3 types: clathrin, COP I, COP II,
• most of coated vesicles bud only from specific regions of a membrane
• coating is made up of a cage of proteins facing the cytosol

Question 19

clathrin-coated vesicles

Answer 19

• clathrin subunits form complexes called triskelion
• each of 3 heavy and 3 light chains
• basket like cage
• secretory and endocytic pathways

Question 19

vesicle fusion

Answer 19

• fusion process to the target membrane is regulated by the snare proteins

Question 20

COP-coated vesicles

Answer 20

• heptameric protein complex involved in inner cell trafficking
• COP I: retrograde pathway, transport
• COP II: anterograde, RER-golgi transport

Question 21

coating: regulation of secretory pathway

Answer 21

• constitutive pathway: molecules released from the TGN to the PM, mostly uncoated, guided by sorting signals to the membrane region
• regulated pathway: molecules released from TGN in clathrin coated vesicles and stored in cytoplasm as larger secretory granules, guided by specific signals (e.g. hormones) to make them fuse with PM

Question 22

cells w lots of vesicles

Answer 22

- secretory cells - lining epithelia - cuboidal cells of PCT epithelium

Question 23

endocytosis

Answer 23

- receptor mediated endocytosis (RME) = clathrin-mediated endocytosis - simulated cells display large number of projections - receptor-mediated entry of specific molecules (hormones, abs LDLs - clathrin coated vesicles

Question 24

ways of fluid/molecule uptake

Answer 24

- RME - pinocytosis - phagocytosis

Question 25

phagocytosis

Answer 25

- ingestion of large particles - bacteria - into large phagosomes - non specific but receptor mediated - un-coated vesicles but actin-dependent

Question 26

pinocytosis

Answer 26

- constitutive uptake of fluids or small molecules - uncoated vesicles

Question 27

endosomal compartments and the lysosomes

Answer 27

- pinocytic vesicles lose their clathrin coats and fuse with early endosomes - early endosomes: system of vesicles and tubules located near the plasma membrane sorting out endocytic material - if contents require degradation it will be transferred to a late endosome

Question 28

progressive acidification of the endosomal compartments

Answer 28

- early to late endosome mature into lysosome - pH 6.2 to 4.7

Question 29

lysosomes

Answer 29

- acidic vesicles with digestive enzymes - digest worn out organelles, food particles, engulfed viruses, bacteria

Question 30

cells having lots of endosomes

Answer 30

- immunity cells

Question 31

lysosomal exocytosis

Answer 31

- process leading to secretion of lysosomal content - lysosome fusion with PM - important mechanism of cellular clearance necessary to maintain cell fitness

Question 32

autophagic machinery

Answer 32

- also involved in unconventional protein secretion and autophagy-dependent secretion - fundamental mechanisms for toxic protein disposal, immune signalling and pathogen surveillance

Question 33

cell communication

Answer 33

- vesicles budding blebbing

Question 34

exosomes

Answer 34

- derive from multi-vesicular bodies - size, content, functional and source heterogenity - release is physiologically modulated

Question 35

types of molecules on, in exosomes

Answer 35

- integrin: cell adhesion - immunnimodulatory - antigen presentation MVB exosomes biogenesis - tetraspanins - lipid anchors, surface proteoglycans - membrane transport - contanin proteins, RNA, DNA, amino acids, metabolites

Question 36

exosome functions

Answer 36

- regulation of gene transcription and translation - survival and proliferation - reproduction and development - angiogenesis and wound healing - waste management - host-microbiome interaction and viral immunity - metabolic reprogramming and regulation - cellular migration and metastatic disease - cellular differentiation and neoplasia - apoptosis - receptor-ligand signalling - balance of immune response and regulation of central and peripheral immunity

Question 37

tumour-derived exosomes

Answer 37

- molecular and genetic messages from tumor cells to normal or other abnormal cells residing at close or distant sites. -found in all body fluids

Question 38

hyper/distrophic mice: experimental design

Answer 38

1. serum collection and EV isolation 2. miRNA isolation and analysis 3. identification or miRNA that promotes myogenesis 4. production of EVs carrying that miRNAs 5.insert into dis/atrophic mice