Neuropeptides and peptide hormones are important cell-cell signaling molecules that mediate many physiological processes. Unlike classic neurotransmitters, peptides undergo cell-type-specific post-translational modifications that affect their biological activity. To enable the identification of the peptide repertoire of a genetically defined cell type, we generated mice with a conditional disruption of the gene for carboxypeptidase E (Cpe), an essential neuropeptide-processing enzyme. The loss of Cpe leads to accumulation of neuropeptide precursors containing C-terminal basic residues, which serve as tags for affinity purification. The purified peptides are subsequently identified using quantitative peptidomics, thereby revealing the specific forms of neuropeptides in cells with the disrupted Cpe gene. To validate the method, we used mice expressing Cre recombinase under the proopiomelanocortin (Pomc) promoter and analyzed hypothalamic and pituitary extracts, detecting peptides derived from proopiomelanocortin (as expected) and also proSAAS in POMC neurons. This technique enables the analyses of specific forms of peptides in any Cre-expressing cell type.

神经肽和肽激素是介导许多生理过程的重要细胞间信号分子。与经典的神经递质不同，肽经历了影响其生物活性的细胞类型特异性翻译后修饰。为了能够识别遗传定义的细胞类型的肽库，我们生成了条件性破坏羧肽酶 E (Cpe) 基因的小鼠，羧肽酶 E ( Cpe ) 是一种必需的神经肽加工酶。Cpe的损失导致含有 C 末端碱性残基的神经肽前体的积累，作为亲和纯化的标签。随后使用定量肽组学鉴定纯化的肽，从而揭示具有破坏的Cpe基因的细胞中神经肽的特定形式。为了验证该方法，我们使用在阿片黑皮质素原 ( Pomc ) 启动子下表达 Cre 重组酶的小鼠，并分析下丘脑和垂体提取物，检测源自阿片黑皮质素原的肽（如预期的那样）以及 POMC 神经元中的 proSAAS。该技术可以分析任何表达 Cre 的细胞类型中特定形式的肽。