Asymptomatic Alzheimer's Disease (AsymAD) is a preclinical stage of Alzheimer's Disease (AD) identified by amyloid plaques and neurofibrillary tangles in cognitively normal individuals and offers esse Show more
Asymptomatic Alzheimer's Disease (AsymAD) is a preclinical stage of Alzheimer's Disease (AD) identified by amyloid plaques and neurofibrillary tangles in cognitively normal individuals and offers essential understanding for early diagnosis and treatment of AD. To uncover molecular insights into AsymAD, RNA sequencing (RNA-seq) datasets from two different consortia, ROSMAP (Religious Orders Study and Memory and Aging Project) and MSBB (Mount Sinai Brain Bank), were investigated. The individuals in the datasets were grouped into AD and AsymAD based on clinical and neuropathological criteria. Differentially expressed genes (DEGs), differentially expressed transcripts (DETs), and differentially used transcripts (DUTs) were identified between AD and AsymAD samples. The results were interpreted through functional enrichment analysis and compared with the predefined lists of AD-related and learning-memory-cognition-related genes, and genes from an independent mouse dataset. The genes from the list of DEGs, DETs and DUTs were mapped onto a human protein-protein interaction network, revealing subnetworks associated with AsymAD. This led to the discovery of biomarker candidate genes: NRXN3, DGKB, ADAMTS2, GNG4, ENPP5, PCOLCE, COL25A1, COL26A1, MRPL1, and MRPL30. This study introduces an innovative approach by including DETs and DUTs in the analyses, beyond the standard focus on DEGs, pointing out comprehensive insights into the molecular mechanisms of AsymAD. In addition, combining the results of the subnetwork analysis from DEGs, DETs, and DUTs provided a new perspective to AsymAD and resulted in the discovery of further important genes, which can pave the way for early detection and intervention of AD. Show less
In humans, 15 genes encode the class B1 family of GPCRs, which are polypeptide hormone receptors characterized by having a large N-terminal extracellular domain (ECD) and receive signals from outside Show more
In humans, 15 genes encode the class B1 family of GPCRs, which are polypeptide hormone receptors characterized by having a large N-terminal extracellular domain (ECD) and receive signals from outside the cell to activate cellular response. For example, the insulinotropic polypeptide (GIP) stimulates the glucose-dependent insulinotropic polypeptide receptor (GIPR), while the glucagon receptor (GCGR) responds to glucagon by increasing blood glucose levels and promoting the breakdown of liver glycogen to induce the production of insulin. The glucagon-like peptides 1 and 2 (GLP-1 and GLP-2) elicit a response from glucagon-like peptide receptor types 1 and 2 (GLP1R and GLP2R), respectively. Since these receptors are implicated in the pathogenesis of diabetes, studying their activation is crucial for the development of effective therapies for the condition. With more structural information being revealed by experimental methods such as X-ray crystallography, cryo-EM, and NMR, the activation mechanism of class B1 GPCRs becomes unraveled. The available crystal and cryo-EM structures reveal that class B1 GPCRs follow a two-step model for peptide binding and receptor activation. The regions close to the C-termini of hormones interact with the N-terminal ECD of the receptor while the regions close to the N-terminus of the peptide interact with the TM domain and transmit signals. This review highlights the structural details of class B1 GPCRs and their conformational changes following activation. The roles of MD simulation in characterizing those conformational changes are briefly discussed, providing insights into the potential structural exploration for future ligand designs. Show less