PMID- 28700649
OWN - NLM
STAT- MEDLINE
DCOM- 20170925
LR  - 20181113
IS  - 1932-6203 (Electronic)
IS  - 1932-6203 (Linking)
VI  - 12
IP  - 7
DP  - 2017
TI  - Autophagy mediates cell cycle response by regulating nucleocytoplasmic transport 
      of PAX6 in limbal stem cells under ultraviolet-A stress.
PG  - e0180868
LID - 10.1371/journal.pone.0180868 [doi]
LID - e0180868
AB  - Limbal stem cells (LSC) account for homeostasis and regeneration of corneal 
      epithelium. Solar ultraviolet A (UVA) is the major source causing oxidative 
      damage in the ocular surface. Autophagy, a lysosomal degradation mechanism, is 
      essential for physiologic function and stress defense of stem cells. PAX6, a 
      master transcription factor governing corneal homeostasis by regulating cell 
      cycle and cell fate of LSC, responds to oxidative stress by nucleocytoplasmic 
      shuttling. Impaired autophagy and deregulated PAX6 have been reported in 
      oxidative stress-related ocular surface disorders. We hypothesize a functional 
      role for autophagy and PAX6 in LSC's stress response to UVA. Therefore, human LSC 
      colonies were irradiated with a sub-lethal dose of UVA and autophagic activity 
      and intracellular reactive oxygen species (ROS) were measured by CYTO-ID assay 
      and CM-H2DCFDA live staining, respectively. Following UVA irradiation, the 
      percentage of autophagic cells significantly increased in LSC colonies while 
      intracellular ROS levels remained unaffected. siRNA-mediated knockdown (KD) of 
      ATG7 abolished UVA-induced autophagy and led to an excessive accumulation of ROS. 
      Upon UVA exposure, LSCs displayed nuclear-to-cytoplasmic translocation of PAX6, 
      while ATG7KD or antioxidant pretreatment largely attenuated the intracellular 
      trafficking event. Immunofluorescence showing downregulation of proliferative 
      marker PCNA and induction of cell cycle regulator p21 indicates cell cycle arrest 
      in UVA-irradiated LSC. Abolishing autophagy, adenoviral-assisted restoration of 
      nuclear PAX6 or antioxidant pretreatment abrogated the UVA-induced cell cycle 
      arrest. Adenoviral expression of an ectopic PAX gene, PAX7, did not affect UVA 
      cell cycle response. Furthermore, knocking down PAX6 attenuated the cell cycle 
      progression of irradiated ATG7KD LSC by de-repressing p21 expression. 
      Collectively, our data suggest a crosstalk between autophagy and PAX6 in 
      regulating cell cycle response of ocular progenitors under UVA stress. Autophagy 
      deficiency leads to impaired intracellular trafficking of PAX6, perturbed redox 
      balance and uncurbed cell cycle progression in UVA-stressed LSCs. The coupling of 
      autophagic machinery and PAX6 in cell cycle regulation represents an attractive 
      therapeutic target for hyperproliferative ocular surface disorders associated 
      with solar radiation.
FAU - Laggner, Maria
AU  - Laggner M
AD  - Department of Ophthalmology & Optometry, Medical University of Vienna, Vienna, 
      Austria.
FAU - Pollreisz, Andreas
AU  - Pollreisz A
AD  - Department of Ophthalmology & Optometry, Medical University of Vienna, Vienna, 
      Austria.
FAU - Schmidinger, Gerald
AU  - Schmidinger G
AD  - Department of Ophthalmology & Optometry, Medical University of Vienna, Vienna, 
      Austria.
FAU - Schmidt-Erfurth, Ursula
AU  - Schmidt-Erfurth U
AD  - Department of Ophthalmology & Optometry, Medical University of Vienna, Vienna, 
      Austria.
FAU - Chen, Ying-Ting
AU  - Chen YT
AD  - Department of Ophthalmology & Optometry, Medical University of Vienna, Vienna, 
      Austria.
LA  - eng
PT  - Journal Article
DEP - 20170710
PL  - United States
TA  - PLoS One
JT  - PloS one
JID - 101285081
RN  - 0 (PAX6 Transcription Factor)
RN  - 0 (PAX7 Transcription Factor)
RN  - 0 (PAX7 protein, human)
RN  - 0 (Reactive Oxygen Species)
SB  - IM
MH  - Active Transport, Cell Nucleus/genetics/*physiology
MH  - Autophagosomes/metabolism/radiation effects
MH  - Autophagy/genetics/*physiology
MH  - Cell Cycle/genetics/*physiology
MH  - Cells, Cultured
MH  - Humans
MH  - Microscopy, Confocal
MH  - PAX6 Transcription Factor/genetics/metabolism
MH  - PAX7 Transcription Factor/genetics/metabolism
MH  - Reactive Oxygen Species/metabolism
MH  - Reverse Transcriptase Polymerase Chain Reaction
MH  - Signal Transduction/radiation effects
MH  - Stem Cells/*cytology/*metabolism/radiation effects
MH  - *Ultraviolet Rays
PMC - PMC5507275
COIS- Competing Interests: The authors have declared that no competing interests exist.
EDAT- 2017/07/13 06:00
MHDA- 2017/09/26 06:00
PMCR- 2017/07/10
CRDT- 2017/07/13 06:00
PHST- 2016/09/13 00:00 [received]
PHST- 2017/06/22 00:00 [accepted]
PHST- 2017/07/13 06:00 [entrez]
PHST- 2017/07/13 06:00 [pubmed]
PHST- 2017/09/26 06:00 [medline]
PHST- 2017/07/10 00:00 [pmc-release]
AID - PONE-D-16-36755 [pii]
AID - 10.1371/journal.pone.0180868 [doi]
PST - epublish
SO  - PLoS One. 2017 Jul 10;12(7):e0180868. doi: 10.1371/journal.pone.0180868. 
      eCollection 2017.