Cardiac contractile strength is recognised as being highly pH-sensitive, but less is known about the influence of pH on cardiac gene expression, which may become relevant in response to changes in myocardial metabolism or vascularization during development or disease. We sought evidence for pH-responsive cardiac genes, and a physiological context for this form of transcriptional regulation. pHLIP, a peptide-based reporter of acidity, revealed a non-uniform pH landscape in early-postnatal myocardium, dissipating in later life. pH-responsive differentially expressed genes (pH-DEGs) were identified by transcriptomics of neonatal cardiomyocytes cultured over a range of pH. Enrichment analysis indicated “striated muscle contraction” as a pH-responsive biological process. Label-free proteomics verified fifty-four pH-responsive gene-products, including contractile elements and the adaptor protein CRIP2. Using transcriptional assays, acidity was found to reduce p300/CBP acetylase activity and, its a functional readout, inhibit myocardin, a co-activator of cardiac gene expression. In cultured myocytes, acid-inhibition of p300/CBP reduced H3K27 acetylation, as demonstrated by chromatin immunoprecipitation. H3K27ac levels were more strongly reduced at promoters of acid-downregulated DEGs, implicating an epigenetic mechanism of pH-sensitive gene expression. By tandem cytoplasmic/nuclear pH imaging, the cardiac nucleus was found to exercise a degree of control over its pH through Na⁺/H⁺ exchangers at the nuclear envelope. Thus, we describe how extracellular pH signals gain access to the nucleus and regulate the expression of a subset of cardiac genes, notably those coding for contractile proteins and CRIP2. Acting as a proxy of a well-perfused myocardium, alkaline conditions are permissive for expressing genes related to the contractile apparatus.

心脏收缩强度被认为对 pH 值高度敏感，但人们对 pH 值对心脏基因表达的影响知之甚少，这可能与发育或疾病期间心肌代谢或血管形成的变化有关。我们寻找 pH 反应心脏基因的证据，以及这种形式的转录调节的生理背景。PHLIP 是一种基于肽的酸度报告基因，它揭示了产后早期心肌中 pH 值不均匀的情况，并在以后的生活中消散。通过在一定 pH 范围内培养的新生儿心肌细胞的转录组学鉴定 pH 响应差异表达基因 (pH-DEG)。富集分析表明“横纹肌收缩”是一种 pH 响应生物过程。无标记蛋白质组学验证了 54 种 pH 响应基因产物，包括收缩元件和衔接蛋白 CRIP2。使用转录测定，发现酸度会降低 p300/CBP 乙酰化酶活性，并且其功能读数会抑制心肌素，心肌素是心脏基因表达的共激活剂。在培养的肌细胞中，p300/CBP 的酸抑制减少了 H3K27 乙酰化，染色质免疫沉淀证明了这一点。H3K27ac 水平在酸下调的 DEG 的启动子处更强烈地降低，暗示 pH 敏感基因表达的表观遗传机制。通过串联细胞质/核 pH 成像，发现心脏核通过 Na 对其 pH 进行一定程度的控制 心脏基因表达的共激活剂。在培养的肌细胞中，p300/CBP 的酸抑制减少了 H3K27 乙酰化，染色质免疫沉淀证明了这一点。H3K27ac 水平在酸下调的 DEG 的启动子处更强烈地降低，暗示 pH 敏感基因表达的表观遗传机制。通过串联细胞质/核 pH 成像，发现心脏核通过 Na 对其 pH 进行一定程度的控制 心脏基因表达的共激活剂。在培养的肌细胞中，p300/CBP 的酸抑制减少了 H3K27 乙酰化，染色质免疫沉淀证明了这一点。H3K27ac 水平在酸下调的 DEG 的启动子处更强烈地降低，暗示 pH 敏感基因表达的表观遗传机制。通过串联细胞质/核 pH 成像，发现心脏核通过 Na 对其 pH 进行一定程度的控制⁺ /H ⁺核包膜处的交换器。因此，我们描述了细胞外 pH 信号如何进入细胞核并调节心脏基因子集的表达，特别是那些编码收缩蛋白和 CRIP2 的基因。作为灌注良好的心肌的代表，碱性条件允许表达与收缩装置相关的基因。