Phospholipase C gamma-2 (PLCγ2)-dependent calcium (Ca2+) oscillations are indispensable for nuclear factor of activated T-cells, cytoplasmic 1 (NFATc1) activation and downstream gene transcription driving osteoclastogenesis during skeletal remodeling and pathological bone loss. Here we describe, to our knowledge, the first known function of transmembrane protein 178 (Tmem178), a PLCγ2 downstream target gene, as a critical modulator of the NFATc1 axis. In surprising contrast to the osteopetrotic phenotype of PLCγ2-/- mice, Tmem178-/- mice are osteopenic in basal conditions and are more susceptible to inflammatory bone loss, owing to enhanced osteoclast formation. Mechanistically, Tmem178 localizes to the ER membrane and regulates RANKL-induced Ca2+ fluxes, thus controlling NFATc1 induction. Importantly, down-regulation of Tmem178 is observed in human CD14+ monocytes exposed to plasma from systemic juvenile idiopathic arthritis patients. Similar to the mouse model, reduced Tmem178 expression in human cells correlates with excessive osteoclastogenesis. In sum, these findings identify an essential role for Tmem178 to maintain skeletal mass and limit pathological bone loss.

Original languageEnglish
Pages (from-to)15654-15659
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number51
StatePublished - Dec 22 2015


  • Calcium
  • NFATc1
  • Osteoclasts
  • SJIA
  • Tmem178


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