We examined whether alteration of PP2A C alpha expression in osteoblasts is involved in osteoclast differentiation. Reduction of PP2A C alpha in MC3T3-E1 cells (shPP2A) decreased receptor activator of nuclear factor kappa B ligand (RANKL) expression and increased osteoprotegerin (OPG) expression. The conditioned medium from shPP2A cells failed to induce NFATc1 as well as the expression of osteoclast marker genes cathepsin K and osteoclast-associated receptor (OSCAR) in bone marrow macrophage cells. Treatment of bone marrow macrophage cells with the conditioned medium from shPP2A cells impaired osteoclastogenesis. These results suggest that alteration of PP2A C alpha expression in osteoblasts modulates the expressions of RANKL and OPG, which are involved in osteoclastogenesis via the NFATc1 transcription factor. (C) 2012 Federation of European Biochemical Societies. Published by Elsevier B. V. All rights reserved.