Cytoophidium assembly reflects upregulation of IMPDH activity

Chia Chun Chang, Wei Cheng Lin, Li Mei Pai, Hsuan Shu Lee, Shinn Chih Wu, Shih Torng Ding, Ji Long Liu*, Li Ying Sung

*Corresponding author for this work

Research output: Contribution to journalJournal Article peer-review

66 Scopus citations


Cytidine triphosphate synthase (CTPS) and inosine monophosphate dehydrogenase (IMPDH) (both of which have two isoforms) can form fiber-like subcellular structures termed 'cytoophidia' under certain circumstances in mammalian cells. Although it has been shown that filamentation of CTPS downregulates its activity by disturbing conformational changes, the activity of IMPDH within cytoophidia is still unclear. Most previous IMPDH cytoophidium studies were performed under conditions involving inhibitors that impair GTP synthesis. Here, we show that IMPDH forms cytoophidia without inhibition of GTP synthesis. First, we find that an elevated intracellular CTP concentration or treatment with 3'-deazauridine, a CTPS inhibitor, promotes IMPDH cytoophidium formation and increases the intracellular GTP pool size. Moreover, restriction of cell growth triggers the disassembly of IMPDH cytoophidia, implying that their presence is correlated with active cell metabolism. Finally, we show that the presence of IMPDH cytoophidia in mouse pancreatic islet cells might correlate with nutrient uptake in the animal. Collectively, our findings reveal that formation of IMPDH cytoophidia reflects upregulation of purine nucleotide synthesis, suggesting that the IMPDH cytoophidium plays a role distinct from that of the CTPS cytoophidium in controlling intracellular nucleotide homeostasis.

Original languageEnglish
Pages (from-to)3550-3555
Number of pages6
JournalJournal of Cell Science
Issue number19
StatePublished - 2015

Bibliographical note

Publisher Copyright:
© 2015.


  • CTPS
  • Cytoophidium
  • Nucleotide


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