Glucose metabolism and Influenza

Question 1

What happens when you increase glucose levels?

Answer 1

Increases Influenza A viral infection of MDCK cells: higher accumulation of viral protein within cells, especially HA and higher % of infected cells

Question 2

What inhibits Influenza A viral infection?

Answer 2

Inhibition of glycolytic enzyme HEXOKINASE –> disassembly of V-ATPase, also inhibition of V-ATPase by certain drugs (e.g. Bafilomycin)

Question 3

What bypasses V-ATPase disassembly (and inhibition of Influenza A infection?)

Answer 3

ATP

Question 4

What correlates with Influenza A infection?

Answer 4

State of V-ATPase assembly

Question 5

What are Influenza viruses?

Answer 5

Respiratory viruses, members of the Orthomyxovirus family

Question 6

What mediates Influenza viral infection?

Answer 6

2 viral proteins: HEMAGGLUTININ (HA) and MATRIX PROTEIN 2 (M2)

Question 7

What does HA do?

Answer 7

Binds to sialic acid residues on cell surface –> endocytosis into and endocytic vesicle

Question 8

How is the pH in the endocytic vesicle (endosome)?

Answer 8

ACIDIC

Question 9

What happens when the pH is acidic within the endosome?

Answer 9

2 things happen: 1) HA changes conformation and fuses viral envelope + endosome membrane and 2) M2 proton channel activates and transports protons –> viral core

Question 10

What happens when there are protons inside the viral core?

Answer 10

Lowers pH within the virion –> viral uncoating –> viral genome is transported from the virion –>cytosol

Question 11

What is V-ATPase?

Answer 11

Vacuolar-type H+ ATPase (proton pump): multi-molecular protein complex with a peripheral and an integral domains

Question 12

Where is V-ATPase located?

Answer 12

Plasma membrane, endosomal membrane and other intracellular compartments of our cells

Question 13

How does V-ATPase favors Influenza viral infection?

Answer 13

By keeping an acidic pH within the endosome which favors viral release

Question 14

What does V-ATPase do inside the cells?

Answer 14

Binds ATP –> Hydrolysis + tranports protons from cytoplasm –> lumen of endosomes/organelles –> lowers pH inside these intracellular compartments which is necessary for multiple cellular processes

Question 15

What are the domains of V-ATPase?

Answer 15

Peripheral V1 –> subunits A,B,C,D,E,F,G

Integral V0 subcomplex –> subunits a,c,d,e

Question 16

How is V-ATPase activity regulated?

Answer 16

Through disassembly of V1 and V0 domains to regulate pH levels of endosomes/organelles

Question 17

What causes disassembly of V-ATPase?

Answer 17

GLUCOSE DEPLETION –> decreased glycolysis –> decreased ATP levels

Question 18

What causes assembly of V-ATPase?

Answer 18

GLUCOSE REPLETION –> increased glycolysis –> sufficient ATP levels (V-ATPase is ATP dependent) –> pump activated –> + acidification

Question 19

How does glucose stimulates V-ATPase activity as per recent research?

Answer 19

Via Phosphatidylinositol 3-kinase signaling pathway and direct physical interaction of glycolytic enzymes and subunits of V-ATPase

Question 20

What glycolytic enzymes interact with subunits of V-ATPase as per recent research?

Answer 20

Phosphofructokinase 1 (PFK-1) (mediates step 3) + a subunit AND Aldolase (mediates step 4) + a,B and E subunits

Question 21

How does glucose reduction and/or inhibition of glycolysis reduce influenza viral infection?

Answer 21

V-ATPase disassembly –> reduce acidification of endosomes –> inhibits influenza M2 and activities –> inhibits influenza viral REPLICATION

Question 22

Problem with antiviral drugs for influenza?

Answer 22

Target viral proteins: Neuraminidase (NA) and M2, but they lose effectiveness as the virus mutates

Question 23

What is the 1st enzyme of glycolysis?

Answer 23

Hexokinase

Question 24

What is the % of viral infection reduction when inhibiting Glycolysis?

Answer 24

80-90%!

Question 25

What represents the viral genome of Influenza virus?

Answer 25

viral ribonucleoprotein (vRNP) complexes

Question 26

What promotes low acidic pH within the endosome?

Answer 26

V-ATPase

Question 27

Where does the virus containing endosome transported to initially?

Answer 27

Periphery of nucleus

Question 28

What specific subunits of V-ATPase are involved in Influenza viral infection?

Answer 28

V1 domain: A,B,C

V0 domain: b, c, d1

Question 29

What subunit seems to have specificity for Influenza virus as per research?

Answer 29

V0d1, Influenza virus seems to manipulate this subunit to stimulate endosome acidification at the nuclear periphery

Question 30

What is Glycolysis?

Answer 30

Process by which glucose is metabolized to generate a net gain of 2 ATP, 2 NADH+ (nicotinamide adenine dinucleotide), and 2 molecules of pyruvate

Question 31

What happens to Pyruvate molecules?

Answer 31

They are further metabolized to produce more ATP

Question 32

What activated V-ATPase?

Answer 32

ATP, which binds to the catalytic sites on the A and B subunits

Question 33

Is glycolysis absolutely required for V-ATPase activation?

Answer 33

No, pump can still be activated as long as additional ATP is available from other sources

Question 34

What happens in diabetic patients?

Answer 34

Will likely have more severe viral infections and Influenza symptoms

Question 35

What happens when cells are changed from a high glucose medium to a low one?

Answer 35

They become LESS SUSCEPTIBLE to infection by Influenza virus!

Question 36

What is this research proving?

Answer 36

Decreasing glucose and/or inhibiting glycolysis may be a way to reduce influenza viral infection in mammals (and humans too!)