BACKGROUND Inhibitor of MyoD family A (I-mfa) is a cytosolic protein. Its function in kidney is unknown. The aim of the present study was to examine the regulatory role of I-mfa on glomerular filtration rate (GFR). METHODS GFR was measured by transdermal measurement of FITC-sinitrin clearance in conscious wild type (WT) and I-mfa knockout (KO) mice. Cell contractility was assessed in a single human or mouse mesangial cell. Single cell RNA sequence (scRNA-seq), Western blot, and Ca2+ imaging were used to evaluate the effects of I-mfa on TRPCs at messenger, protein and functional levels in MCs. RESULTS In KO mice, GFR was significantly lower than that in WT mice. In WT mice, knocking down I-mfa selectively in mesangial cells using targeted nanoparticle/siRNA delivery system significantly decreased GFR. In human mesangial cells, overexpression of I-mfa significantly blunted the Ang II-stimulated contraction, and knockdown of I-mfa significantly enhanced the contractile response. Consistently, the Ang II-induced contraction was significantly augmented in primary mesangial cells isolated from KO mice. The exaggerated response was restored by re-introducing I-mfa. Furthermore, scRNA-seq showed an increase in trpc1 messenger and Western blot showed an increase in TRPC1 protein abundance in I-mfa KO mouse mesangial cells. TRPC1 protein abundance was decreased in HEK cells overexpressing I-mfa. Ca2+ imaging experiments showed that downregulation of I-mfa significantly enhanced Ang II-stimulated Ca2+ entry in human mesangial cells. Finally, TRPC1 inhibitor, Pico145 significantly blunted Ang II-induced mesangial cell contraction. CONCLUSIONS I-mfa positively regulated GFR by decreasing mesangial cell contractile function through inhibition of TRPC1-mediated Ca2+ signaling.

中文翻译：

---

I-MFA、系膜细胞 TRPC1 通道和肾小球滤过率的调节。


背景 MyoD 家族 A 抑制剂 （I-mfa） 是一种胞质蛋白。它在肾脏中的功能尚不清楚。本研究的目的是检查 I-mfa 对肾小球滤过率 （GFR） 的调节作用。方法 通过透皮测量清醒野生型 （WT） 和 I-mfa 敲除 （KO） 小鼠的 FITC-sinitrin 清除率来测量 GFR。在单个人或小鼠系膜细胞中评估细胞收缩力。采用单细胞 RNA 序列 （scRNA-seq） 、Western blot 和 Ca2+ 成像评价 I-mfa 对 MCs 信使、蛋白和功能水平 TRPCs 的影响。结果 KO 小鼠 GFR 显著低于 WT 小鼠。在 WT 小鼠中，使用靶向纳米颗粒/siRNA 递送系统选择性敲低系膜细胞中的 I-mfa 可显著降低 GFR。在人系膜细胞中，I-mfa 的过表达显着减弱了 Ang II 刺激的收缩，而 I-mfa 的敲除显着增强了收缩反应。一致地，Ang II 诱导的收缩在 KO 小鼠分离的原代系膜细胞中显着增强。通过重新引入 I-mfa 来恢复夸张的反应。此外，scRNA-seq 显示 trpc1 信使增加，Western blot 显示 I-mfa KO 小鼠系膜细胞中 TRPC1 蛋白丰度增加。在过表达 I-mfa 的 HEK 细胞中，TRPC1 蛋白丰度降低。Ca2 + 成像实验显示，I-mfa 的下调显着增强了 Ang II 刺激的 Ca2 + 进入人系膜细胞。最后，TRPC1 抑制剂 Pico145 显着减弱了 Ang II 诱导的系膜细胞收缩。结论 I-mfa 通过抑制 TRPC1 介导的 Ca2+ 信号传导降低系膜细胞收缩功能，正向调节 GFR。