Age-related impairment of macroautophagy/autophagy and loss of cardiac tissue homeostasis contribute significantly to cardiovascular diseases later in life. MTOR (mechanistic target of rapamycin kinase) signaling is the most well-known regulator of autophagy, cellular homeostasis, and longevity. The MTOR signaling consists of two structurally and functionally distinct multiprotein complexes, MTORC1 and MTORC2. While MTORC1 is well characterized but the role of MTORC2 in aging and autophagy remains poorly understood. Here we identified TGFB-INHB/activin signaling as a novel upstream regulator of MTORC2 to control autophagy and cardiac health during aging. Using Drosophila heart as a model system, we show that cardiac-specific knockdown of TGFB-INHB/activin-like protein daw induces autophagy and alleviates age-related heart dysfunction, including cardiac arrhythmias and bradycardia. Interestingly, the downregulation of daw activates TORC2 signaling to regulate cardiac autophagy. Activation of TORC2 alone through overexpressing its subunit protein rictor promotes autophagic flux and preserves cardiac function with aging. In contrast, activation of TORC1 does not block autophagy induction in daw knockdown flies. Lastly, either daw knockdown or rictor overexpression in fly hearts prolongs lifespan, suggesting that manipulation of these pathways in the heart has systemic effects on longevity control. Thus, our studies discover the TGFB-INHB/activin-mediated inhibition of TORC2 as a novel mechanism for age-dependent decreases in autophagic activity and cardiac health.

Abbreviations: AI: arrhythmia index; BafA1: bafilomycin A₁; BMP: bone morphogenetic protein; CQ: chloroquine; CVD: cardiovascular diseases; DI: diastolic interval; ER: endoplasmic reticulum; HP: heart period; HR: heart rate; MTOR: mechanistic target of rapamycin kinase; NGS: normal goat serum; PBST: PBS with 0.1% Triton X-100; PDPK1: 3-phosphoinositide dependent protein kinase 1; RICTOR: RPTOR independent companion of MTOR complex 2; ROI: region of interest; ROUT: robust regression and outlier removal; ROS: reactive oxygen species; R-SMAD: receptor-activated SMAD; SI: systolic interval; SOHA: semi-automatic optical heartbeat analysis; TGFB: transformation growth factor beta; TSC1: TSC complex subunit 1

与年龄相关的巨自噬/自噬损伤和心脏组织稳态的丧失在以后的生活中显着导致心血管疾病。MTOR（雷帕霉素激酶的机械靶标）信号是自噬、细胞稳态和寿命最广为人知的调节器。MTOR 信号传导由两个结构和功能不同的多蛋白复合物 MTORC1 和 MTORC2 组成。虽然 MTORC1 的特征很好，但 MTORC2 在衰老和自噬中的作用仍然知之甚少。在这里，我们将 TGFB-INHB/激活素信号确定为 MTORC2 的新型上游调节器，以控制衰老过程中的自噬和心脏健康。使用果蝇心脏作为模型系统，我们表明心脏特异性敲低 TGFB-INHB/激活素样蛋白 daw 诱导自噬并减轻与年龄相关的心脏功能障碍，包括心律失常和心动过缓。有趣的是，daw的下调激活了 TORC2 信号传导以调节心脏自噬。通过过表达其亚基蛋白 rictor 单独激活 TORC2 可促进自噬通量并随着衰老保持心脏功能。相比之下，TORC1 的激活不会阻止daw击倒果蝇的自噬诱导。最后，要么daw击倒要么rictor果蝇心脏中的过度表达可延长寿命，这表明对心脏中这些通路的操纵对寿命控制具有系统性影响。因此，我们的研究发现 TGFB-INHB/激活素介导的 TORC2 抑制是年龄依赖性自噬活性和心脏健康下降的新机制。

缩写： AI：心律失常指数；BafA1：巴弗洛霉素A ₁；BMP：骨形态发生蛋白；CQ：氯喹；CVD：心血管疾病；DI：舒张间隔；ER：内质网；HP：心脏周期；HR：心率；MTOR：雷帕霉素激酶的机制靶点；NGS：正常山羊血清；PBST：含有 0.1% Triton X-100 的 PBS；PDPK1：3-磷酸肌醇依赖性蛋白激酶 1；RICTOR：MTOR complex 2 的 RPTOR 独立伴侣；ROI：感兴趣的区域；ROUT：稳健回归和异常值去除；ROS：活性氧；R-SMAD：受体激活的SMAD；SI：收缩期；SOHA：半自动光学心跳分析；TGFB：转化生长因子β；TSC1：TSC 复合亚基 1