Department of Biochemistry and Molecular Biology, The University of Texas Medical Branch, Galveston, Texas, USA.
Department of Comparative Medicine and Center for Lung Biology, University of Washington, Seattle, WA, USA.
J Leukoc Biol. 2021 Apr;109(4):777-791. doi: 10.1002/JLB.3A0820-207R. Epub 2020 Sep 2.
Chemokines play a crucial role in combating microbial infection by recruiting blood neutrophils to infected tissue. In mice, the chemokines Cxcl1/KC and Cxcl2/MIP2 fulfill this role. Cxcl1 and Cxcl2 exist as monomers and dimers, and exert their function by activating the Cxcr2 receptor and binding glycosaminoglycans (GAGs). Here, we characterized Cxcr2 G protein and β-arrestin activities, and GAG heparan sulfate (HS) interactions of Cxcl1 and Cxcl2 and of the trapped dimeric variants. To understand how Cxcr2 and GAG interactions impact in vivo function, we characterized their neutrophil recruitment activity to the peritoneum, Cxcr2 and CD11b levels on peritoneal and blood neutrophils, and transport profiles out of the peritoneum. Cxcl2 variants compared with Cxcl1 variants were more potent for Cxcr2 activity. Native Cxcl1 compared with native Cxcl2 and dimers compared with native proteins bound HS with higher affinity. Interestingly, recruitment activity between native Cxcl1 and Cxcl2, between dimers, and between the native protein and the dimer could be similar or very different depending on the dose or the time point. These data indicate that peritoneal neutrophil recruitment cannot be solely attributed to Cxcr2 or GAG interactions, and that the relationship between recruited neutrophils, Cxcr2 activation, GAG interactions, and chemokine levels is complex and highly context dependent. We propose that the ability of Cxcl1 and Cxcl2 to reversibly exist as monomers and dimers and differences in their Cxcr2 activity and GAG interactions coordinate neutrophil recruitment and activation, which play a critical role for successful resolution of inflammation.
趋化因子在招募血液中性粒细胞到感染组织中以抵抗微生物感染方面发挥着至关重要的作用。在小鼠中，趋化因子 Cxcl1/KC 和 Cxcl2/MIP2 发挥了这一作用。Cxcl1 和 Cxcl2 以单体和二聚体的形式存在，通过激活 Cxcr2 受体并结合糖胺聚糖 (GAG) 来发挥其功能。在这里，我们对 Cxcr2 G 蛋白和 β-arrestin 活性以及 Cxcl1 和 Cxcl2 及其捕获的二聚体变体与 GAG 硫酸乙酰肝素 (HS) 的相互作用进行了表征。为了了解 Cxcr2 和 GAG 相互作用如何影响体内功能，我们对其向腹膜中性粒细胞的募集活性、腹膜和血液中性粒细胞上的 Cxcr2 和 CD11b 水平以及从腹膜中的转运情况进行了表征。与 Cxcl1 变体相比，Cxcl2 变体对 Cxcr2 活性的作用更强。与天然 Cxcl2 相比，天然 Cxcl1 与 HS 的结合亲和力更高，与二聚体相比，天然蛋白与二聚体的结合亲和力更高。有趣的是，天然 Cxcl1 与 Cxcl2 之间、二聚体之间以及天然蛋白与二聚体之间的募集活性可能相似或非常不同，具体取决于剂量或时间点。这些数据表明，腹膜中性粒细胞的募集不能仅仅归因于 Cxcr2 或 GAG 相互作用，并且募集的中性粒细胞、Cxcr2 激活、GAG 相互作用和趋化因子水平之间的关系是复杂的，高度依赖于上下文。我们提出，Cxcl1 和 Cxcl2 能够可逆地存在为单体和二聚体，以及它们在 Cxcr2 活性和 GAG 相互作用方面的差异，协调中性粒细胞的募集和激活，这对炎症的成功解决起着至关重要的作用。
