R-spondin3（RSPO3）是血管生成和血管发育的关键蛋白，RSPO3显著增强Wnt/β-catenin信号，促内皮细胞增殖、迁移及新生血管形成[1,2]。除Wnt/β-catenin信号外，Akt-mTOR的激活也对血管生成至关重要。研究表明RSPO3可激活Akt-mTOR通路[3]。但Akt-mTOR在RSPO3诱导的血管生成中的作用及相关分子机制并不明确。

课题组多年来研究证实G蛋白抑制性α亚单位1和3（Gαi1/3蛋白）是多个因子下游信号转导的关键蛋白。在生长因子刺激下，Gαi1/3和受体酪氨酸激酶（RTKs）等受体结合介导下游信号转导（Protein & Cell 2022b [4]，Science Signaling 2009[5]，Oncogene 2018, 2021^[6,7]，IJBS 2022[8]，Theranostics2018，2021a/b[9-11]等论文）。例如，前期研究发现敲减、敲除Gαi1/3后，BDNF信号传导受阻，海马神经元树突数目及单位距离的树突棘的数目均显著减少（PNAS 2018[12]，Highlight by PNAS[13]）。课题前期已证明Gαi1/3是促血管生成的关键信号蛋白。在VEGF刺激下，Gαi1/3促VEGFR2的内吞、下游Akt-mTOR转导和血管生成[11]。此外，课题组最新研究还发现磷酸烯醇式丙酮酸羧激酶1（PCK1）通过促进Gαi3表达和Akt-mTOR激活促血管生成（Science Advances 2022[14]）。

2022年8月13日，苏州大学小草嫩芽研究视频、苏州大学附属第二医院神经疾病中心曹聪课题组在Protein & Cell （IF = 15.3）发表了题为“Gαi1/3 mediation of Akt-mTOR activation is important for RSPO3-induced angiogenesis”文章，该研究揭示了Gαi1/3介导RSPO3诱导的Akt-mTOR通路激活、促血管新生。

研究发现在体外培养的人脐静脉内皮细胞（HUVECs）和人脑微血管内皮细胞（HCMEC/D3）中，RSOP3诱导LGR4-Gαi1/3-Gab1信号复合体的形成，介导下游Akt-mTOR的激活。RSPO3诱导的Akt-mTOR激活独立于Wnt/β-catenin信号通路。在HUVECs和HCMEC/D3细胞中，敲减Gαi1/3显著抑制RSPO3诱导的内皮细胞迁移、增殖和体外成管。而Gαi1/3过表达则增强了RSPO3诱导的体外促血管新生作用。C57小鼠内皮细胞特异性敲减Gαi1/3后显著抑制RSPO3过表达诱导的Akt-mTOR激活和小鼠视网膜血管新生；而内皮细胞特异性过表达Gαi1/3显著促进视网膜血管新生。综上，Gαi1/3介导Akt-mTOR激活对RSPO3诱导的血管生成至关重要。

原文链接：https://doi.org/10.1093/procel/pwac035

参考文献：

1. Jin YR, Yoon JK. The R-spondin family of proteins: emerging regulators of WNT signaling. Int J Biochem Cell Biol 2012; 44(12): 2278-87.

2. Kazanskaya O, Ohkawara B, Heroult M, Wu W, Maltry N, Augustin HG, Niehrs C. The Wnt signaling regulator R-spondin 3 promotes angioblast and vascular development. Development 2008; 135(22): 3655-64.

3. Ter Steege EJ, Bakker ERM. The role of R-spondin proteins in cancer biology. Oncogene 2021; 40(47): 6469-78.

4. Liu F, Chen G, Zhou L, Wang Y, Zhang Z, Qin X, Cao C. YME1L overexpression exerts pro-tumorigenic activity in glioma by promoting Gαi1 expression and Akt activation. Protein Cell 2022.

5. Cao C, Huang X, Han Y, Wan Y, Birnbaumer L, Feng GS, Marshall J, Jiang M, Chu WM. Galpha(i1) and Galpha(i3) are required for epidermal growth factor-mediated activation of the Akt-mTORC1 pathway. Sci Signal 2009; 2(68): ra17.

6. Liu YY, Chen MB, Cheng L, Zhang ZQ, Yu ZQ, Jiang Q, Chen G, Cao C. microRNA-200a downregulation in human glioma leads to Galphai1 over-expression, Akt activation, and cell proliferation. Oncogene 2018; 37(21): 2890-902.

7. Lv Y, Wang Y, Song Y, Wang SS, Cheng KW, Zhang ZQ, Yao J, Zhou LN, Ling ZY, Cao C. LncRNA PINK1-AS promotes G alpha i1-driven gastric cancer tumorigenesis by sponging microRNA-200a. Oncogene 2021; 40(22): 3826-44.

8. Bian ZJ, Shan HJ, Zhu YR, Shi C, Chen MB, Huang YM, Wang XD, Zhou XZ, Cao C. Identification of Galphai3 as a promising target for osteosarcoma treatment. Int J Biol Sci 2022; 18(4): 1508-20.

9. Wang Y, Liu YY, Chen MB, Cheng KW, Qi LN, Zhang ZQ, Peng Y, Li KR, Liu F, Chen G, et al. Neuronal-driven glioma growth requires Galphai1 and Galphai3. Theranostics 2021; 11(17): 8535-49.

10. Bai JY, Li Y, Xue GH, Li KR, Zheng YF, Zhang ZQ, Jiang Q, Liu YY, Zhou XZ, Cao C. Requirement of Galphai1 and Galphai3 in interleukin-4-induced signaling, macrophage M2 polarization and allergic asthma response. Theranostics 2021; 11(10): 4894-909.

11. Sun J, Huang W, Yang SF, Zhang XP, Yu Q, Zhang ZQ, Yao J, Li KR, Jiang Q, Cao C. Galphai1 and Galphai3mediate VEGF-induced VEGFR2 endocytosis, signaling and angiogenesis. Theranostics 2018; 8(17): 4695-709.

12. Marshall J, Zhou XZ, Chen G, Yang SQ, Li Y, Wang Y, Zhang ZQ, Jiang Q, Birnbaumer L, Cao C. Antidepression action of BDNF requires and is mimicked by Galphai1/3 expression in the hippocampus. Proc Natl Acad Sci U S A 2018; 115(15): E3549-E58.

13. Licznerski P, Jonas EA. BDNF signaling: Harnessing stress to battle mood disorder. Proc Natl Acad Sci U S A 2018; 115(15): 3742-4.

14. Yao J, Wu XY, Yu Q, Yang SF, Yuan J, Zhang ZQ, Xue JS, Jiang Q, Chen MB, Xue GH, et al. The requirement of phosphoenolpyruvate carboxykinase 1 for angiogenesis in vitro and in vivo. Sci Adv 2022; 8(21): eabn6928.