Jansen Margo I, Hrncir Haley, MacKenzie-Graham Allan, Waschek James A, Brinkman Judith, Bradfield Laura A, Withana Minduli, Musumeci Giuseppe, D'Agata Velia, Castorina Alessandro
Laboratory of Cellular and Molecular Neuroscience, School of Life Sciences, Faculty of Science, University of Technology Sydney, Sydney, NSW, Australia.
Department of Neurology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, USA.
Life Sci. 2025 Oct 1;378:123843. doi: 10.1016/j.lfs.2025.123843. Epub 2025 Jul 6.
Pituitary Adenylate Cyclase-Activating Polypeptide (PACAP) is an endogenous neuropeptide of the central nervous system (CNS), whose biological activities are mediated via three G protein-coupled receptors PAC1, VPAC1, and VPAC2. While its neuroprotective functions are well-characterised, the role of PAC1 receptor-specific signalling in neuronal plasticity remains insufficiently understood. This study aimed to define the contribution of PAC1 signalling in excitatory pyramidal neurons across brain regions critical for cognitive and motor functions.
We employed a tamoxifen-inducible, conditional knockout mouse model to delete the PAC1 receptor gene (Adcyap1r1) specifically in Camk2a-expressing excitatory neurons. The model was crossed with Thy1-YFP and Thy1-mitoCFP reporter lines to enable high-resolution imaging of neuronal structures and mitochondria in the cortex and hippocampus. Behavioural assessments, molecular analyses, and confocal imaging were conducted to evaluate structural, functional, and biochemical consequences of PAC1 deletion.
Loss of PAC1 in Camk2a neurons resulted in spatial memory deficits and locomotor impairments. These were associated with elevated expression of neuronal nitric oxide synthase (nNOS) and GAD65/67, reduced CREB phosphorylation at Ser133, diminished dendritic spine density, and decreased mitochondrial content. The most pronounced effects were observed in the CA1 region of the hippocampus.
Our findings establish PAC1 as a key modulator of synaptic integrity, neuronal plasticity, and energy homeostasis in excitatory neurons. These insights underscore PAC1's potential as a therapeutic target in neurological disorders characterised by cognitive decline and synaptic dysfunction.
垂体腺苷酸环化酶激活多肽（PACAP）是中枢神经系统（CNS）的一种内源性神经肽，其生物活性通过三种G蛋白偶联受体PAC1、VPAC1和VPAC2介导。虽然其神经保护功能已得到充分表征，但PAC1受体特异性信号在神经元可塑性中的作用仍未得到充分理解。本研究旨在确定PAC1信号在对认知和运动功能至关重要的脑区兴奋性锥体神经元中的作用。
我们采用了一种他莫昔芬诱导的条件性敲除小鼠模型，以特异性删除在表达CaMK2α的兴奋性神经元中的PAC1受体基因（Adcyap1r1）。该模型与Thy1-YFP和Thy1-线粒体CFP报告基因系杂交，以实现对皮质和海马中神经元结构和线粒体的高分辨率成像。进行行为评估、分子分析和共聚焦成像，以评估PAC1缺失的结构、功能和生化后果。
CaMK2α神经元中PAC1的缺失导致空间记忆缺陷和运动障碍。这些与神经元型一氧化氮合酶（nNOS）和GAD65/67的表达升高、Ser133处CREB磷酸化减少、树突棘密度降低以及线粒体含量减少有关。在海马体的CA1区域观察到最明显的影响。
我们的研究结果表明PAC1是兴奋性神经元中突触完整性、神经元可塑性和能量稳态的关键调节因子。这些见解强调了PAC1作为以认知衰退和突触功能障碍为特征的神经系统疾病治疗靶点的潜力。
