Cell attachment to the extracellular matrix induces proteasomal degradation of p21CIP1 via Cdc42/Rac1 signaling
Cell attachment to the extracellular matrix induces proteasomal degradation of p21CIP1 via Cdc42/Rac1 signaling
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DOI：
10.1128/mcb.22.13.4587-4597.2002
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发表时间：
2002-07-01
影响因子：
5.3
通讯作者：
Strömblad, S
中科院分区：
文献类型：
--
作者：
Bao, WJ;Thullberg, M;Strömblad, S
细胞周期蛋白依赖性激酶2（Cdk 2）抑制剂p21（CIP 1）和p27（KIP 1）在细胞增殖过程中受到锚定的负调控，但尚不清楚整合素信号传导如何影响这些Cdk 2抑制剂。在这里，我们证明，整合素连接导致快速减少p21（CIP 1）和p27（KIP 1）蛋白水平在三种不同的细胞类型后，附着到各种细胞外基质（ECM）蛋白，包括纤连蛋白（FN），或固定的激动抗整合素单克隆抗体。细胞粘附FN并不迅速影响p21（CIp 1）mRNA水平，而p21（CIp 1）的蛋白质稳定性下降。重要的是，下调的p21（CIP 1）和p27（KIP 1）被完全阻断三个不同的蛋白酶体抑制剂，表明整合素连接诱导这些Cdk 2抑制剂的蛋白酶体降解。有趣的是，ECM诱导的泛素化缺陷型p21（CIP 1）突变体（p21 K6 R）的蛋白酶体蛋白水解也发生了，表明p21（CIP 1）的蛋白酶体降解是泛素独立的。伴随着我们的发现，小GTP酶Cdc 42和Rac 1被激活的连接到FN，组成型活性（ca）Cdc 42和ca Rac 1促进下调p21（CIP 1）。然而，显性失活（dn）Cdc 42和do Rac 1突变体阻断了锚定诱导的p21降解（CIP 1），表明整合素诱导的Cdc 42/Rac 1信号通路激活了p21（CIP 1）的蛋白酶体降解。我们的研究结果表明，整合素调节的蛋白酶体蛋白水解可能有助于锚定依赖性细胞周期控制。
The cyclin-dependent kinase 2 (Cdk2) inhibitors p21(CIP1) and p27(KIP1) are negatively regulated by anchorage during cell proliferation, but it is unclear how integrin signaling may affect these Cdk2 inhibitors. Here, we demonstrate that integrin ligation led to rapid reduction of p21(CIp1) and p27(KIP1) protein levels in three distinct cell types upon attachment to various extracellular matrix (ECM) proteins, including fibronectin (FN), or to immobilized agonistic anti-integrin monoclonal antibodies. Cell attachment to FN did not rapidly influence p21(CIp1) mRNA levels, while the protein stability of p21(CIp1) was decreased. Importantly, the down-regulation of p21(CIP1) and p27(KIP1) was completely blocked by three distinct proteasome inhibitors, demonstrating that integrin ligation induced proteasomal degradation of these Cdk2 inhibitors. Interestingly, ECM-induced proteasomal proteolysis of a ubiquitination-deficient p21(CIP1) mutant (p21K6R) also occurred, showing that the proteasomal degradation of p21(CIP1) was ubiquitin independent. Concomitant with our finding that the small GTPases Cdc42 and Rac1 were activated by attachment to FN, constitutively active (ca) Cdc42 and ca Rac1 promoted down-regulation of p21(CIP1). However, dominant negative (dn) Cdc42 and do Rac1 mutants blocked the anchorage-induced degradation of p21(CIP1), suggesting that an integrin-induced Cdc42/Rac1 signaling pathway activates proteasomal degradation of p21(CIP1). Our results indicate that integrin-regulated proteasomal proteolysis might contribute to anchorage-dependent cell cycle control.