Identification of an alternatively spliced variant of Ca2+-promoted Ras inactivator as a possible regulator of RANKL shedding
Identification of an alternatively spliced variant of Ca2+-promoted Ras inactivator as a possible regulator of RANKL shedding
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DOI：
10.1074/jbc.m507000200
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发表时间：
2005-12-16
影响因子：
4.8
通讯作者：
Tanaka, S
中科院分区：
文献类型：
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作者：
Hikita, A;Kadono, Y;Tanaka, S
NF-κ B配体受体激活剂（RANKL）是破骨细胞生成的关键调节因子，其合成为膜锚定蛋白，并通过胞外域脱落切割成可溶性形式。我们开发了一种测定系统来鉴定调节RANKL脱落的分子。使用该系统，我们发现在原代成骨细胞中表达的Ca 2+促进的Ras灭活剂（卡普里）的剪接变体Delta卡普里促进RANKL脱落。野生型卡普里是Ras GTP酶激活蛋白（GAP）家族的成员，抑制Ca 2+依赖性Ras激活，而Delta卡普里在GAP相关结构域中缺少一个外显子，激活Ras途径。Delta卡普里或Ras组成型活性形式的过表达上调了基质金属蛋白酶14（MMP 14）的表达水平，MMP 14直接切割RANKL的胞外域，而通过表达组成型活性Mek 1激活Erk并不影响MMP 14表达或RANKL脱落。这些结果表明，Delta卡普里可能是RANKL脱落的调节因子，通过Ras信号级联而非Erk通路调节MMP 14表达。
The receptor activator of NF-kappa B ligand (RANKL), a critical regulator of osteoclastogenesis, is synthesized as a membrane-anchored protein and cleaved into a soluble form by ectodomain shedding. We developed an assay system to identify molecules regulating the RANKL shedding. Using this system, we found that a splice variant of Ca2+-promoted Ras inactivator ( CAPRI), Delta CAPRI, which is expressed in primary osteoblasts, promoted the RANKL shedding. The wild type CAPRI is a member of the Ras GTPase-activating protein ( GAP) family and suppresses Ca2+- dependent Ras activation, whereas Delta CAPRI, which lacks one exon in the GAP-related domain, activated the Ras pathway. Overexpression of Delta CAPRI or a constitutive active form of Ras up-regulated the expression level of matrix-metalloproteinase 14 (MMP14), which directly cleaves the ectodomain of RANKL, whereas Erk activation by expressing the constitutive active Mek1 did not affect the MMP14 expression or RANKL shedding. These results suggest that Delta CAPRI is a possible regulator of RANKL shedding by modulating MMP14 expression through Ras signaling cascades other than the Erk pathway.