👤 María Mercedes Bigi

Mitogen-activated protein kinase (MAPK) phosphatases [MKPs, also known as dual-specificity phosphatases (DUSPs)] regulate MAPKs -key mediators of cellular processes such as proliferation, differentiation, and survival- by dephosphorylating the threonine and tyrosine residues required for MAPK activation. MKP-3/DUSP6 is an ERK-selective phosphatase that has also been reported to regulate the transcription factor FOXO1. The full-length MKP-3 transcript has been shown to encode the MKP-3L protein, whereas alternative splicing gives rise to the shorter isoform MKP-3S. However, the available information regarding the functional differences between these variants is limited. By combining biochemical and bioinformatic approaches, we demonstrate that these isoforms differ significantly in subcellular localization and enzymatic activity. Structural analysis and molecular docking reveal that while MKP-3S retains functional binding domains and recognizes ERK2 similarly to the full-length isoform. However, the absence of critical catalytic motifs in MKP-3S leads to a structural uncoupling where the protein retains its ability to bind ERK2 but fails to induce dephosphorylation, suggesting a non-canonical role as a molecular scaffold. The results obtained demonstrate significant variations in subcellular localization, enzymatic activity, and the capacity to modulate FOXO1 transcriptional activity. This, in turn, affects the expression of genes such as p21. In conclusion, the findings indicate that MKP-3 variants exhibit distinct functional behaviours, which may result in differential regulation of a wide range of cellular processes. Show less

High cholesterol levels are a risk factor for the development of Alzheimer's disease. Experiments investigating the influence of cholesterol on the proteolytic processing of the amyloid precursor protein (APP) by the β-secretase Bace1 and on their proximity in cells have led to conflicting results. By using a fluorescence bioassay coupled with flow cytometry we found a direct correlation between the increase in membrane cholesterol amount and the degree of APP shedding in living human neuroblastoma cells. Analogue results were obtained for cells overexpressing an APP mutant that cannot be processed by α-secretase, highlighting the major influence of cholesterol enrichment on the cleavage of APP carried out by Bace1. By contrast, the cholesterol content was not correlated with changes in membrane dynamics of APP and Bace1 analyzed with single molecule tracking, indicating that the effect of cholesterol enrichment on APP processing by Bace1 is uncoupled from changes in their lateral diffusion. Show less

Livestock guardian (LGD) and herding shepherd (HSD) dogs have distinct morphological and behavioural characteristics, long selected by farmers and breeders, to accomplish different tasks. This study aimed to find the genomic regions that best differentiate and characterise Italian LGD and HSD. Genomic data of 158 dogs of four LGD and five HSD breeds, obtained with the 170K canine SNPchip, were collected. The two groups were compared using F Show less