Guthridge Mark A, Barry Emma F, Felquer Fernando A, McClure Barbara J, Stomski Frank C, Ramshaw Hayley, Lopez Angel F
Cytokine Receptor Laboratory, Department of Human Immunology, Institute of Medical and Veterinary Science, Frome Rd, Adelaide, South Australia, Australia 5000.
Blood. 2004 Feb 1;103(3):820-7. doi: 10.1182/blood-2003-06-1999. Epub 2003 Aug 14.
We have recently identified a novel mechanism of hematopoietic cell survival that involves site-specific serine phosphorylation of the common beta subunit (beta(c)) of the granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin-3 (IL-3), and IL-5 receptors. However, the downstream components of this pathway are not known, nor is its relationship to survival signals triggered by tyrosine phosphorylation of the receptor clear. We have now found that phosphorylation of Ser585 of beta(c) in response to GM-CSF recruited 14-3-3 and phosphatidyl inositol 3-OH kinase (PI 3-kinase) to the receptor, while phosphorylation of the neighboring Tyr577 within this "viability domain" promoted the activation of both Src homology and collagen (Shc) and Ras. These are independent processes as demonstrated by the intact reactivity of phosphospecific anti-Ser585 and anti-Tyr577 antibodies on the cytotoxic T-lymphocyte-ecotrophic retroviral receptor neomycin (CTL-EN) mutants beta(c)Tyr577Phe and beta(c)Ser585Gly, respectively. Importantly, while mutants in which either Ser585 (beta(c)Ser585Gly) or all tyrosines (beta(c)F8) were substituted showed a defect in Akt phosphorylation, nuclear factor kappaB (NF-kappaB) activation, bcl-2 induction, and cell survival, the mutant beta(c)Tyr577Phe was defective in Shc, Ras, and extracellular signal-related kinase (ERK) activation, but supported CTL-EN cell survival in response to GM-CSF. These results demonstrate that both serine and tyrosine phosphorylation pathways play a role in hematopoietic cell survival, are initially independent of each other, and converge on NF-kappaB to promote bcl-2 expression.
我们最近发现了一种造血细胞存活的新机制，该机制涉及粒细胞-巨噬细胞集落刺激因子（GM-CSF）、白细胞介素-3（IL-3）和IL-5受体的共同β亚基（β(c)）的位点特异性丝氨酸磷酸化。然而，该途径的下游成分尚不清楚，其与受体酪氨酸磷酸化触发的存活信号之间的关系也不明确。我们现在发现，响应GM-CSF时β(c)的Ser585磷酸化会将14-3-3和磷脂酰肌醇3-羟基激酶（PI 3-激酶）募集到受体上，而在这个“存活结构域”内相邻的Tyr577磷酸化则促进了Src同源和胶原蛋白（Shc）以及Ras的激活。这些是独立的过程，磷酸化特异性抗Ser585和抗Tyr577抗体分别对细胞毒性T淋巴细胞-嗜生态逆转录病毒受体新霉素（CTL-EN）突变体β(c)Tyr577Phe和β(c)Ser585Gly具有完整的反应性，这证明了这一点。重要的是，虽然Ser585（β(c)Ser585Gly）或所有酪氨酸（β(c)F8）被取代的突变体在Akt磷酸化、核因子κB（NF-κB）激活、bcl-2诱导和细胞存活方面存在缺陷，但突变体β(c)Tyr577Phe在Shc、Ras和细胞外信号调节激酶（ERK）激活方面存在缺陷，但在响应GM-CSF时支持CTL-EN细胞存活。这些结果表明，丝氨酸和酪氨酸磷酸化途径在造血细胞存活中都起作用，最初彼此独立，并汇聚于NF-κB以促进bcl-2表达。
