FFK506-Binding Protein 12.6/1b, a negative regulator of [Ca2+], rescues memory and restores genomic regulation in the hippocampus of aging rats

Hippocampal overexpression of FK506-binding protein 12.6/1b (FKBP1b), a negative regulator of ryanodine receptor Ca2+ release, reverses aging-induced memory impairment and neuronal Ca2+ dysregulation. Here, we test the hypothesis that FKBP1b also can protect downstream transcriptional networks from aging-induced dysregulation. We gave hippocampal microinjections of FKBP1b-expressing viral vector to male rats at either 13-months-of-age (long-term) or 19-months-of-age (short-term) and tested memory performance in the Morris water maze at 21-months-of-age. Aged rats treated short- or long-term with FKBP1b substantially outperformed age-matched vector controls and performed similarly to each other and young controls. Transcriptional profiling in the same animals identified 2342 genes whose hippocampal expression was up-/down-regulated in aged controls vs. young controls (the aging effect). Of these aging-dependent genes, 876 (37%) also showed altered expression in aged FKBP1b-treated rats compared to aged controls, with FKBP1b restoring expression of essentially all such genes (872/876, 99.5%) in the direction opposite the aging effect and closer to levels in young controls. This inverse relationship between the aging and FKBP1b effects suggests that the aging effects arise from FKBP1b deficiency. Functional category analysis revealed that genes downregulated with aging and restored by FKBP1b associated predominantly with diverse brain structure categories, including cytoskeleton, membrane channels and extracellular region. Conversely, genes upregulated with aging but not restored by FKBP1b associated primarily with glial-neuroinflammatory, ribosomal and lysosomal categories. Immunohistochemistry confirmed aging-induced rarefaction, and FKBP1b-mediated restoration, of neuronal microtubular structure. Thus, a previously-unrecognized genomic network modulating diverse brain structural processes is dysregulated by aging and restored by FKBP1b overexpression.FK506结合蛋白12.6/1b（FK506-binding protein 12.6/1b，FKBP1b）是雷诺丁受体钙释放的负调控因子，其在海马体中的过表达可逆转衰老诱导的记忆损伤与神经元钙稳态失调。本研究旨在验证FKBP1b亦可保护下游转录网络免受衰老引发的稳态失衡这一假说。我们分别于13月龄（长期干预组）与19月龄（短期干预组）的雄性大鼠海马体中微注射表达FKBP1b的病毒载体，并于21月龄时通过莫里斯水迷宫（Morris water maze）检测其记忆能力。结果显示，接受短期或长期FKBP1b干预的衰老大鼠，其表现显著优于同年龄段的空载体对照组，且两组干预大鼠的表现彼此相近，同时与年轻对照组无显著差异。对同一批实验动物的海马组织进行转录组分析后，我们共鉴定出2342个基因，其在衰老大鼠与年轻大鼠海马中的表达存在显著上调或下调（即衰老效应）。在上述衰老相关差异基因中，有876个（占比37%）在FKBP1b干预的衰老大鼠中同样出现表达异常；其中，FKBP1b可使99.5%（872/876）的此类基因表达逆转衰老诱导的变化方向，并使其表达水平趋近于年轻对照组。衰老效应与FKBP1b干预效应之间的这种负相关关系表明，衰老相关的基因表达紊乱源于FKBP1b的表达不足。功能富集分析显示，随衰老下调且可被FKBP1b恢复的基因，主要富集于多种脑结构相关类别，包括细胞骨架、膜通道及细胞外区域。反之，随衰老上调且无法被FKBP1b恢复的基因，则主要与胶质细胞神经炎症、核糖体及溶酶体功能相关。免疫组织化学（immunohistochemistry）实验证实，衰老可诱导神经元微管结构稀疏，而FKBP1b过表达可逆转这一变化。综上，此前未被认知的、调控多种脑结构过程的基因组网络，可因衰老出现稳态失衡，而FKBP1b过表达可对其进行修复。