Regulation of osteoclast differentiation and function by the CaMK-CREB pathway

K Sato, A Suematsu, T Nakashima… - Nature medicine, 2006 - nature.com
K Sato, A Suematsu, T Nakashima, S Takemoto-Kimura, K Aoki, Y Morishita, H Asahara…
Nature medicine, 2006nature.com
Abstract Calcium (Ca2+) signaling is essential for a variety of cellular responses and higher
biological functions. Ca2+/calmodulin-dependent kinases (CaMKs) and the phosphatase
calcineurin activate distinct downstream pathways that are mediated by the transcription
factors cAMP response element (CRE)-binding protein (CREB) and nuclear factor of
activated T cells (NFAT), respectively. The importance of the calcineurin-NFAT pathway in
bone metabolism has been demonstrated in osteoclasts, osteoblasts and chondrocytes …
Abstract
Calcium (Ca2+) signaling is essential for a variety of cellular responses and higher biological functions. Ca2+/calmodulin-dependent kinases (CaMKs) and the phosphatase calcineurin activate distinct downstream pathways that are mediated by the transcription factors cAMP response element (CRE)-binding protein (CREB) and nuclear factor of activated T cells (NFAT), respectively. The importance of the calcineurin-NFAT pathway in bone metabolism has been demonstrated in osteoclasts, osteoblasts and chondrocytes,,,. However, the contribution of the CaMK-CREB pathway is poorly understood, partly because of the difficulty of dissecting the functions of homologous family members,,. Here we show that the CaMKIV-CREB pathway is crucial for osteoclast differentiation and function. Pharmacological inhibition of CaMKs as well as the genetic ablation of Camk4 reduced CREB phosphorylation and downregulated the expression of c-Fos, which is required for the induction of NFATc1 (the master transcription factor for osteoclastogenesis,) that is activated by receptor activator of NF-κB ligand (RANKL). Furthermore, CREB together with NFATc1 induced the expression of specific genes expressed by differentiated osteoclasts. Thus, the CaMK-CREB pathway biphasically functions to regulate the transcriptional program of osteoclastic bone resorption, by not only enhancing induction of NFATc1 but also facilitating NFATc1-dependent gene regulation once its expression is induced. This provides a molecular basis for a new therapeutic strategy for bone diseases.
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