Tao Yu, Liu Muyi, Siebert Garland, Das-Earl Paromita, Ibrahim Deena, Crowe Nicole, Zheng Suilan, Ma Rong
Department of Physiology and Anatomy, University of North Texas HSC, Fort Worth, Texas.
Department of Microbiology, Immunology and Genetics, University of North Texas HSC, Fort Worth, Texas.
J Am Soc Nephrol. 2025 Apr 1;36(4):614-627. doi: 10.1681/ASN.0000000533. Epub 2024 Oct 24.
I-mfa is a multifunctional cytosolic protein and its function in kidney is unknown. The major finding in the present study was that I-mfa promoted glomerular filtration rate in both male and female mice. I-mfa suppressed contractile function of both human and mouse glomerular mesangial cells by decreasing TRPC1 channel protein abundance.
Inhibitor of MyoD family A (I-mfa) is a cytosolic protein. Its function in the kidney is unknown. The aim of this study was to examine the regulatory role of I-mfa on GFR.
GFR was measured by transdermal measurement of fluorescein isothiocyanate–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, Western blot, and Ca imaging were used to evaluate the effects of I-mfa on transient receptor potential canonical (TRPCs) at messenger, protein, and functional levels in mesangial cells.
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/small interfering RNA delivery system significantly decreased GFR. In human mesangial cells, overexpression of I-mfa significantly blunted the angiotensin II (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 reintroducing I-mfa. Furthermore, single-cell RNA sequence showed an increase in messenger, and Western blot showed an increase in TRPC1 protein abundance in I-mfa KO mouse mesangial cells. TRPC1 protein abundance was decreased in human embryonic kidney cells overexpressing I-mfa. Ca imaging experiments showed that downregulation of I-mfa significantly enhanced Ang II–stimulated Ca entry in human mesangial cells. Finally, TRPC1 inhibitor Pico145 significantly blunted Ang II–induced mesangial cell contraction.
I-mfa positively regulated GFR by decreasing mesangial cell contractile function through inhibition of TRPC1-mediated Ca signaling.
I-mfa是一种多功能胞质蛋白，其在肾脏中的功能尚不清楚。本研究的主要发现是，I-mfa可提高雄性和雌性小鼠的肾小球滤过率。I-mfa通过降低TRPC1通道蛋白丰度来抑制人和小鼠肾小球系膜细胞的收缩功能。
肌分化因子A抑制剂（I-mfa）是一种胞质蛋白。其在肾脏中的功能尚不清楚。本研究的目的是探讨I-mfa对肾小球滤过率（GFR）的调节作用。
通过对清醒的野生型（WT）和I-mfa基因敲除（KO）小鼠经皮测量异硫氰酸荧光素-西尼trin清除率来测量GFR。在单个原代人或小鼠系膜细胞中评估细胞收缩性。利用单细胞RNA测序、蛋白质印迹法和钙成像技术，在信使、蛋白质和功能水平上评估I-mfa对系膜细胞中瞬时受体电位阳离子通道亚家族C成员1（TRPCs）的影响。
在KO小鼠中，GFR显著低于WT小鼠。在WT小鼠中，使用靶向纳米颗粒/小干扰RNA递送系统在系膜细胞中选择性敲低I-mfa可显著降低GFR。在人系膜细胞中，I-mfa的过表达显著减弱了血管紧张素II（Ang II）刺激的收缩，而I-mfa的敲低则显著增强了收缩反应。同样，从KO小鼠分离的原代系膜细胞中，Ang II诱导的收缩显著增强。通过重新引入I-mfa可恢复过度的反应。此外，单细胞RNA测序显示I-mfa KO小鼠系膜细胞中信使增加，蛋白质印迹法显示TRPC1蛋白丰度增加。在过表达I-mfa的人胚肾细胞中，TRPC1蛋白丰度降低。钙成像实验表明，I-mfa的下调显著增强了Ang II刺激的人系膜细胞中的钙内流。最后，TRPC1抑制剂Pico145显著减弱了Ang II诱导的系膜细胞收缩。
I-mfa通过抑制TRPC1介导的钙信号传导，降低系膜细胞收缩功能，从而对GFR起到正向调节作用。
