Singapore grouper iridovirus (SGIV) induces a type of programmed cell death called parapotosis in host cells. This document summarizes research finding that SGIV activates mitogen-activated protein kinase (MAPK) signaling pathways, including ERK, JNK, and p38 MAPK, to induce parapotosis and facilitate viral replication. Inhibition of the ERK and JNK pathways can delay cytopathic effects and reduce virus production, indicating their role in the viral life cycle. JNK activation in particular promotes viral transcription and protein synthesis. MAPK signaling also modulates the expression of immune genes during infection. Therefore, SGIV utilizes MAPK pathways to induce parapotosis in host cells and

1. Singapore grouper iridovirus (SGIV) induced
parapotosis-like cell death in host cells via the
activation of MAPK signalings
Qiwei Qin
South China Sea Institute of Oceanology
Chinese Academy of Sciences
2013.7.27

2. programmed cell death ， PCD
PCD is natural and genetically regulated process of removing unneeded
or damaged cells, and it plays critical roles in the balance between host
defense and the invading pathogen during pathogen-host co-evolution.
Research background
(Dale E. Bredesen, 2007)

3. Morphological and biochemical characteristics of apoptosis and
parapoptosis (Sperandio et al., 2000)

4. Virus infection induced PCD
Virus infection induced apoptosis. Virus infection induced autophagic PCD
So far, no report on virus infection induced parapoptosis !

5. MAPK signaling pathways and PCD
MAPKs have been identified: extracellular signal-
regulated kinase (ERK), c-Jun N-terminal kinases
(JNK) and p38 MAPK （ Wada et al, 2004 ）。
Mitogen-activated protein
kinase (MAPK) cascades
are evolutionary
conserved intracellular
signaling pathways that
regulate gene expression,
mitosis, proliferation,
metabolism and
programmed cell death.

6. MAPKs and virus infection
MAPK
(Han, Nat Immunol, 2006)
TLR could recognize the PAMPs of pathogens (virus, bacterial) and
trigger the host immune responses, including the activation of MAPK signaling pathways.

7. Virus infection could activate MAPK
pathways in mammalian and humans.
Aquatic animal
viruses activate
MAPK signaling
pathways ？？

8. Iridovirus is one of the most important infectious
pathgens for maricultured grouper, Epinephelus spp ！
Singapore grouper iridovirus (SGIV) isolated from diseased grouper is a
novel species of ranavirus, family iridovidae （ Qin et al., 2003).

9. 1. How the SGIV interact with grouper host cells causing
cell death ？
2 、 What kind of host cell signaling pathways involve in
the virus infection ？

10. Huang et al, Aquaculture, 2009
SGIV infected grouper cells
Lai et al, J Fish Dis. 2008
GIV infected barramundi cells
Apoptosis Non-apoptosis
Whether SGIV infection induced PCD is cell type
dependent ？

11. Research results
1.SGIV infection induced different type of cell death and nucleus
morphology in host and non-host two fish cells
Cell types Characteristics
SGIV-EAGS rounded, congregated, remain attach, condensed
nuclei, non-apoptotic bodies
SGIV-FHM rounded, detached, apoptotic bodies observed

12. Cells Characteristics
SGIV-FHM DNA fragementation, DNA ladder, TUNEL positive
SGIV-EAGS no fragementation,no DNA ladder, TUNEL negetive
DNA fragmentation and DAN content analysis of
SGIV-infected two fish cells

13. SGIV-infectedEAGS:
appearance of cytoplamic
vaculoes, distended endoplasmic
reticulum (ER), large cluster of
swollen mitochondria.
SGIV-FHM:
ER swelling

14. Examination of PS externalization and caspae activities
The exposure of PS on cell surface is a general marker of apoptotic cells. The exposure of PS
only occurred on the FHM cell surface during SGIV infection.
Caspase-3 and -9 were activated in SGIV-infected FHM cells, but not in infected EAGS cells.

15. UV-inactivated SGIV had not effect on EAGS cells, but still evoked obviously
apoptosis in FHM cells.
Virus replication was essential for SGIV induced nonapoptotic cell
death, but not for apoptosis.

16. SGIV infection activated MAPK signaling
molecules in grouper cells
ERK, p38 MAPK and JNK molecules were phosphorylated at the different
stages during SGIV infection in host EAGS cells.

17. Inhibition of ERK and JNK activities could delay the CPE and reduce the virus production.
MAPK signaling pathways were involved in SGIV
replication in grouper host cells

18. Inhibition of JNK pathway could inhibit SGIV gene transcription and
protein synthesis. No obvious changes for inhibition of p38 MAPK.
JNK but not p38 MAPK is important for SGIV
transcription and protein synthesis

19. SGIV infection evoked increased the expression of IL-8, IRF-1 and
TNFa, inhibition of JNK resulted in the reduction of 3 immune
genes, inhibition of p38 MAPK only reduced the expression of
Fish immune genes were regulated by MAPKs
IL-8 IRF-1 TNF-a

20. Conclusions
SGIV infection induced nonapoptotic cell death-parapotosis
in grouper host cells.

21. MAPK signaling pathways involved in the SGIV
infection and replication in host cells.
ERK 、 JNK signals are essential for virus replication
and virus induced parapotosis
SGIV-activated MAPK pathways could modulate the expression of
immune genes and inflammatory cytokines

22. Related publications:
1. Huang X., Huang Y., Ouyang Z., Cai J., Qin Q. 2011. J Gen Virol.,
Jun; 92:1292-301.
2. Huang X., Huang Y., Ouyang Z., Xu L, Yan Y, Cui H, Han X, Qin Q.
2011. Apoptosis, Aug;16(8):831-45.

23. 23
Acknowledges: National Basical Research
Program(973 program); NSFC; CAS

24. Thank you very muchThank you very much
for your attentionfor your attention ！！