Expressão e atividade da ADAM10, um biomarcador sérico da doença de Alzheimer, e de suas formas em diferentes frações de células semelhantes a neurônios

Abstract

With the global increase in life expectancy, cases of Alzheimer’s disease (AD), a progressive neurodegeneration associated with cognitive, behavioral, and functional impairments, are also rising. Its main pathophysiological hallmarks are hyperphosphorylated tau protein, which forms intracellular tangles, and β-amyloid (Aβ) peptide, which aggregates extracellularly into amyloid plaques. AD is classified into a biological form (in which biomarkers are present but symptoms are absent) and a clinical form (in which both pathology and deficits are observed). Biomarkers are essential tools for early detection, diagnosis, and treatment evaluation, especially in the early stages of the disease. The most used biomarkers are imaging-based or measure Aβ and tau levels in cerebrospinal fluid, but these methods have limitations, making blood-based biomarkers a promising alternative. ADAM10, the main α-secretase responsible for non-amyloidogenic cleavage of amyloid precursor protein (APP), has been studied as a potential serum biomarker for AD. Our data show that its soluble form has low activity in plasma. Therefore, this study aims to evaluate the expression and activity of ADAM10 forms in cellular fractions to determine the relationship between the protein’s localization and activity. For this, SH-SY5Y neuroblastoma cells were differentiated into neuron-like cells and fractionated into portions containing proteins from the extracellular medium (FS), plasma membrane and cytoplasm (FC), organelle membranes (FM), and nucleus (FN). The protein expression and enzymatic activity of the soluble (sADAM10, cleaved by ADAM9), mature (mADAM10), and immature (proADAM10) forms of ADAM10 were assessed in each fraction. Our results show that sADAM10, located in the extracellular environment, has low activity compared to mADAM10, anchored to the plasma membrane, in neuron-like cells. Additionally, we observed that ADAM9 is predominantly expressed in axons of neurons in mouse brain sections. These findings contribute to a better understanding of ADAM10 biology and support its continued development as a blood-based biomarker for AD.