Dysregulated protein phosphorylation: A determining condition in the continuum of brain aging and Alzheimer's disease

Abstract

Tau hyperphosphorylation is the first step of neurofibrillary tangle (NFT) formation. In the present study, samples of the entorhinal cortex (EC) and frontal cortex area 8 (FC) of cases with NFT pathology classified as stages I-II, III-IV, and V-VI without comorbidities, and of middle-aged (MA) individuals with no NFT pathology, were analyzed by conventional label-free and SWATH-MS (sequential window acquisition of all theoretical fragment ion spectra mass spectrometry) to assess the (phospho)proteomes. The total number of identified dysregulated phosphoproteins was 214 in the EC, 65 of which were dysregulated at the first stages (I-II) of NFT pathology; 167 phosphoproteins were dysregulated in the FC, 81 of them at stages I-II of NFT pathology. A large percentage of dysregulated phosphoproteins were identified in the two regions and at different stages of NFT progression. The main group of dysregulated phosphoproteins was made up of components of the membranes, cytoskeleton, synapses, proteins linked to membrane transport and ion channels, and kinases. The present results show abnormal phosphorylation of proteins at the first stages of NFT pathology in the elderly (in individuals clinically considered representative of normal aging) and sporadic Alzheimer's disease (sAD). Dysregulated protein phosphorylation in the FC precedes the formation of NFTs and SPs. The most active period of dysregulated phosphorylation is at stages III-IV when a subpopulation of individuals might be clinically categorized as suffering from mild cognitive impairment which is a preceding determinant stage Platform of Navarrabiomed is supported by grant PT17/0019/009 to JFI, of the PE I + D+I 2013-2016 funded by ISCIII and FEDER. Part of this work was funded by a grant from the Spanish Ministry of Science Innovation and Universities (Ref. PID2019-110356RB-I00) to JFI and ES, and the Department of Economic and Business Development from the Government of Navarra (Ref. 0011-1411(Ref. 0011- -2020 to ES in the progression to dementia. Altered phosphorylation of selected proteins, carried out by activation of several kinases, may alter membrane and cytoskeletal functions, among them synaptic transmission and membrane/cytoskeleton signaling. Besides their implications in sAD, the present observations suggest a molecular substrate for "benign" cognitive deterioration in "normal" brain aging.

Dysregulated protein phosphorylation in tauopathy

“…The present ndings reveal wide dysregulated protein phosphorylation in P301S transgenic mice that involves numerous proteins associated with membranes and cell membrane tra cking, synapses, neurotransmitter receptors, membrane vesicles linked to endo-and exocytosis, cytoplasmic vesicles, and the cytoskeleton, together with altered phosphorylation of a large number of kinases targeting various substrates. The targets are similar to those identi ed in sAD and GGT [21,23], thus suggesting that abnormal tau, as exempli ed by mutant P301S tau in transgenic mice, is associated with dysregulated protein phosphorylation of key components of membranes and the cytoskeleton, and mediated by abnormal activation of kinases. Alterations of these particular proteins implicate abnormal membrane signalling and cytoskeletal function, altered neurotransmission, and membrane and cytoplasmic vesicle metabolism.…”

“…Other pathways modulating energy metabolism, cell signalling, Golgi apparatus, carbohydrates, and lipids are also targets of dysregulated protein phosphorylation in P301S mice.The present results, together with accompanying immunohistochemical and western blotting studies, show widespread abnormal phosphorylation of proteins, in addition to protein tau, in P301S mice. These observations point to dysregulated protein phosphorylation as a relevant contributory pathogenic component of tauopathies.precedes, in the frontal cortex, the appearance of abnormal β-amyloid and tau deposits in this region [21].Abnormal phosphorylation of various proteins occurs in aging-related tau astrogliopathy (ARTAG) [22].Large-scale (phospho)proteomics also reveals dysregulated protein phosphorylation in globular glial tauopathy (GGT), a rare sporadic and familial tauopathy [23]. Dysregulated protein phosphorylation has also been reported in transgenic mouse models of AD expressing abnormal β-amyloid deposition [24][25][26][27][28][29], but there is little information about differential protein phosphorylation in transgenic models of pure tauopathy [26].…”

“…AD generates, in addition to hyperphosphorylated tau, dysregulated phosphorylation of a large number of proteins [18][19][20]. Differentially regulated phosphoproteins are components of cell membranes and membrane signalling, cytoskeleton, synapses including neurotransmitter receptors, serine-threonine kinases, proteins involved in energy metabolism, and RNA processing and splicing, among others [18, 19,21]. Dysregulated protein phosphorylation in AD occurs at the rst stages of NFT pathology, and Table 1 List of antibodies used for immunohistochemistry and western blotting: 3Rtau: tau with three repeats; 4Rtau: tau with four repeats; AKT1: serine/threonine-protein kinase AKT1; β-actin; CK1-δ: casein kinase δ; eIF2α: eukaryotic initiation factor 2α; GSK β: glycogen synthase kinase 3β; IRE1: inositol-requiring enzyme 1α; LAMP1: lysosomal-associated membrane protein 3; LC3: microtubule-associated protein 1A/1B-light chain 3; MAP2: microtubule-associated protein 2; NFL: neuro lament light molecular weight; p38: p38-kinase; PHF1: anti-paired helical lament 1; PKAα/β: cAMP-dependent protein kinase A; SAPK/JNK: stress-activated protein kinase/Jun amino-terminal kinase; SRC: tyrosine-protein kinase SRC; Tau 5: monoclonal recognizing total tau protein; Tau AT8; Tau C3: tau truncated at aspartic acid 421; Tau MC1: conformation tau; Tau-N: nitrated tau; Tau-P phosphorylated tau.…”

“…precedes, in the frontal cortex, the appearance of abnormal β-amyloid and tau deposits in this region [21].…”

Circulating Low Density Neutrophils Are Associated with Resistance to First-Line Anti-PD1/PDL1 Immunotherapy in Non-Small Cell Lung Cancer

“…Protein concentration was measured using Bradford assay kit (Biorad). MS/MS Library Generation and Quantitative Analysis were performed as previously described [23]. Briefly, 20 μg per sample were be used and the quantitative data obtained was analyzed using Perseus software [24] for statistical analysis and data visualization.…”