NELL-1 increases pre-osteoblast mineralization using both phosphate transporter Pit1 and Pit2

CM Cowan, X Zhang, AW James, TM Kim, N Sun… - Biochemical and …, 2012 - Elsevier
CM Cowan, X Zhang, AW James, TM Kim, N Sun, B Wu, K Ting, C Soo
Biochemical and biophysical research communications, 2012Elsevier
NELL-1 is a potent osteoinductive molecule that enhances bone formation in multiple animal
models through currently unidentified pathways. In the present manuscript, we hypothesized
that NELL-1 may regulate osteogenic differentiation accompanied by alteration of inorganic
phosphate (Pi) entry into the osteoblast via sodium dependent phosphate (NaPi)
transporters. To determine this, MC3T3-E1 pre-osteoblasts were cultured in the presence of
recombinant human (rh) NELL-1 or rhBMP-2. Analysis was performed for intracellular Pi …
NELL-1 is a potent osteoinductive molecule that enhances bone formation in multiple animal models through currently unidentified pathways. In the present manuscript, we hypothesized that NELL-1 may regulate osteogenic differentiation accompanied by alteration of inorganic phosphate (Pi) entry into the osteoblast via sodium dependent phosphate (NaPi) transporters. To determine this, MC3T3-E1 pre-osteoblasts were cultured in the presence of recombinant human (rh)NELL-1 or rhBMP-2. Analysis was performed for intracellular Pi levels through malachite green staining, Pit-1 and Pit-2 expression, and forced upregulation of Pit-1 and Pit-2. Results showed rhNELL-1 to increase MC3T3-E1 matrix mineralization and Pi influx associated with activation of both Pit-1 and Pit-2 channels, with significantly increased Pit-2 production. In contrast, Pi transport elicited by rhBMP-2 showed to be associated with increased Pit-1 production only. Next, neutralizing antibodies against Pit-1 and Pit-2 completely abrogated the Pi influx effect of rhNELL-1, suggesting rhNELL-1 is dependent on both transporters. These results identify one potential mechanism of action for rhNELL-1 induced osteogenesis and highlight a fundamental difference between NELL-1 and BMP-2 signaling.
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