Accumulation of p100, a Precursor of NF-kappa B2, Enhances Osteoblastic Differentiation in Vitro and Bone Formation in Vivo in aly/aly Mice

作者：Seo Yoshinori; Fukushima Hidefumi; Maruyama Toshimasa; Kuroishi Kayoko Nakao; Osawa Kenji; Nagano Kenichi; Aoki Kazuhiro; Weih Falk; Doi Takahiro; Zhang Min; Ohya Keiichi; Katagiri Takenobu; Hosokawa Ryuji; Jimi Eijiro^*

来源：Molecular Endocrinology, 2012, 26(3): 414-422.

DOI：10.1210/me.2011-1241

We previously reported that alymphoplasia (aly/aly) mice, which have a natural loss-of-functions mutation in the Nik gene, which encodes a kinase essential for the processing of p100 to p52 in the alternative nuclear factor-kappa B (NF-kappa B) pathway, show mild osteopetrosis with an increase in several parameters of bone formation: bone formation rate, mineral apposition rate, and osteoblast number. We therefore investigated the molecular mechanisms triggered by the alternative NF-kappa B pathway in the regulation of osteoblast differentiation using primary osteoblasts (POB) prepared from aly/aly mice. Alkaline phosphatase (ALP) activity and mineralization induced by the presence of beta-glycerophosphate and ascorbic acid were enhanced in POB from aly/aly compared with wild-type (WT) mice. Furthermore, osteoblastic differentiation induced by bone morphogenetic protein 2 (BMP2), as shown by ALP activity, mRNA expression of osteocalcin, Id1, Osterix and Runx2, and Sma- and Mad-related protein (Smad)1/5/8 phosphorylation, was also enhanced in POB from aly/aly mice. The ectopic bone formation in vivo that was induced by BMP2 was enhanced in aly/aly mice compared with controls. Transfection of a mutant form of p100, p100 Delta GRR, which cannot be processed to p52, stimulated ALP activity and Smad phosphorylation. In contrast to p100 Delta GRR, overexpression of p52 inhibited these events. Both BMP2-induced ALP activity and Smad phosphorylation were reduced in POB from p100-deficient mice, which carry a homozygous deletion of the COOH-terminal ankyrin repeats of p100 but still express functional p52 protein. p52 and p100 Delta GRR interacted with a BMP receptor, ALK2, in overexpressed COS7 cells and changed the ALK2 protein levels in opposite directions: p52 reduced ALK2 and p100 increased it. Thus, the alternative the NF-kappa B pathway via the processing of p52 from p100 negatively regulates osteoblastic differentiation and bone formation by modifying BMP activity. (Molecular Endocrinology 26: 414-422, 2012)

• 出版日期2012-3