In proliferating cells, centrosomes organize the microtubule network and this function depends on the γ-tubulin ring complex (γTuRC). While in quiescent cells, the mother centriole of the centrosome organizes the formation of primary cilia, which are microtubule-based organelles present in most vertebrate cells. Cilia are involved in many essential signaling pathways and plays important roles in helping cells sense extracellular environment.

The previous study of our laboratory identified that NME7 (non-metastatic cells 7) is a novel γTuRC component, which promotes γTuRC-mediated microtubule nucleation through its kinase action. NME7 is a member of the nucleoside-diphosphate kinase (NDPK) family. nme7 knockout mice exhibit cilia-related defects, including situs inve...[ Read more ]

In proliferating cells, centrosomes organize the microtubule network and this function depends on the γ-tubulin ring complex (γTuRC). While in quiescent cells, the mother centriole of the centrosome organizes the formation of primary cilia, which are microtubule-based organelles present in most vertebrate cells. Cilia are involved in many essential signaling pathways and plays important roles in helping cells sense extracellular environment.

The previous study of our laboratory identified that NME7 (non-metastatic cells 7) is a novel γTuRC component, which promotes γTuRC-mediated microtubule nucleation through its kinase action. NME7 is a member of the nucleoside-diphosphate kinase (NDPK) family. nme7 knockout mice exhibit cilia-related defects, including situs inversus and hydrocephalus. Moreover, we found that NME7 localizes to cilia and is essential for ciliary growth. Considering the NME7’s important role in the events such as microtubule nucleation and ciliogenesis, I identify NME7-binding proteins by mass spectrometry, characterize their interactions with NME7, and uncover the function of these interactions. One of the identified proteins has been reported to block primary cilia assembly in proliferating cells. I found that NME7 and the binding partner have interaction with each other, and the binding protein can also be a competitor for the binding of γTuRC to NME7. Interestingly, the protein level of the binding protein significantly decreased in NME7-depleted cells. I further investigated how NME7 knockdown affects the expression of the binding protein. Protein stability analysis showed that NME7 depletion decreases protein stability of the binding protein. Furthermore, depletion of the binding protein or NME7 resulted in cilia formation in proliferating cells. These results suggest that NME7 may block ciliogenesis in proliferating cells by stabilization of the binding protein. In summary, I provided a series of potential NME7-binding partners which might be essential for the regulation and functional study of NME7.