Biology subjects

Carlsson, A.

Publications and source records attributed to Carlsson, A..

4 recordsLinked to original sources

bioRxiv2026

DNAJB6b: a complete amyloid inhibitor

In Alzheimer's disease (AD), the aggregation of amyloid {beta} (A{beta}) peptides has been linked to disease pathology. Once aggregates have formed, existing fibrils catalyze the formation of new fibrils in a runaway process associated with neuro degeneration. One component of the cellular defense system against amyloid formation is the molecular chaperone DNAJB6b (JB6). JB6 is known to suppress both primary nucleation and fibril-catalyzed secondary nucleation. However, the extent of JB6 binding to A{beta} fibrils and whether this interaction leads to inhibition of fibril elongation also, have not been established. Here, we combine well-characterized aggregation kinetics of A{beta}42 and the knowledge of JB6 self-assembly equilibrium and kinetics, with high-sensitivity HPLC measurements of free JB6 at nanomolar concentrations to determine the affinity of JB6 for A{beta}42 fibrils. We show that JB6 binds to A{beta}42 fibrils with high affinity and that this binding can quantitatively explain the observed elongation inhibition. Diffusion-based techniques reveal that JB6 binds to amyloid intermediates, resulting in potent suppression of amyloid nucleation until the pool of free JB6 is depleted, after which rapid bulk aggregation ensues. Our results provide a mechanistic link between chaperone-fibril binding and amyloid suppression, offering a quantitative framework for understanding how molecular chaperones regulate amyloid formation.

biochemistry↗

bioRxiv2026

ROS Impair Mitophagy via PARylation of PINK1

Mitophagy is the process of selective autophagic clearance of damaged mitochondria and is closely implicated in neurodegenerative disease. PTEN-induced kinase 1 (PINK1) and a RBR E3 ubiquitin-protein ligase (Parkin) constitute a positive feedback loop in mitophagy initiation. It is known that reactive oxygen species (ROS) modulate mitophagy, while the exact regulatory mechanism remains largely elusive. Here, we found that exogenously applied ROS effectively block mitophagy induced by acute mitochondrial damage agents, which could be reversed by antioxidants. Mechanistically, ROS activate poly(ADP-ribose) polymerase 1 (PARP1), and suppression of PARP1 eliminates the inhibitory effect of ROS on mitophagy. Notably, PARP1 directly interacts with PINK1 and mediates its PARylation at residue E417, thereby negatively regulating PINK1 function. Collectively, our study identifies PARylation as a new form of post-translational modification of PINK1 and reveals a novel mechanism underlying the regulatory role of ROS in mitophagy by PARP1 activation and PARylation of PINK1. In briefGao et al. demonstrate that exogenous ROS inhibit mitophagy. Mechanistically, ROS activate PARP1, which mediates PARylation of PINK1, a central regulator of mitophagy, leading to its functional impairment. This study reveals a novel regulatory mechanism of ROS on mitophagy through PARP1 activation and identifies PARylation as a novel form of post-translational modification of PINK1. HighlightsO_LIROS block PINK1-Parkin-mediated mitophagy. C_LIO_LIROS activate PARP1. C_LIO_LIPARP1 suppression eliminates the inhibitory effect of ROS on mitophagy. C_LIO_LIPARylation of PINK1 by PARP1 impairs its activity and mitophagy. C_LI

Cell Biology↗

bioRxiv2021

In vitro experiments and kinetic models of pollen hydration show that MSL8 is not a simple tension-gated osmoregulator

Pollen, a neighbor-less cell that contains the male gametes, undergoes multiple mechanical challenges during plant sexual reproduction, including desiccation and rehydration. It was previously showed that the pollen-specific mechanosensitive ion channel MscS-Like (MSL)8 is essential for pollen survival during hydration and proposed that it functions as a tension-gated osmoregulator. Here we test this hypothesis with a combination of mathematical modeling and laboratory experiments. Time-lapse imaging revealed that wild-type pollen grains swell and then stabilize in volume rapidly during hydration. msl8 mutant pollen grains, however, continue to expand and eventually burst. We found that a mathematical model wherein MSL8 acts as a simple tension-gated osmoregulator does not replicate this behavior. A better fit was obtained from variations of the model wherein MSL8 inactivation is independent of its membrane tension gating threshold or MSL8 strengthens the cell wall without osmotic regulation. Experimental and computational testing of several perturbations, including hydration in an osmolyte-rich solution, hyper-desiccation of the grains, and MSL8-YFP overexpression, indicated that the Cell Wall Strengthening Model best simulated experimental responses. Finally, expression of a non-conducting MSL8 variant did not complement the msl8 overexpansion phenotype. These data indicate that, contrary to our hypothesis and to known MS ion channel function in single-cell systems, MSL8 does not act as a simple membrane tension-gated osmoregulator. Instead, they support a model wherein ion flux through MSL8 is required to alter pollen cell wall properties. These results demonstrate the utility of pollen as a cellular-scale model system and illustrate how mathematical models can correct intuitive hypotheses.

plant biology↗

bioRxiv2017

Clustering of adult-onset diabetes into novel subgroups guides therapy and improves prediction of outcome

BackgroundDiabetes is presently classified into two main forms, type 1 (T1D) and type 2 diabetes (T2D), but especially T2D is highly heterogeneous. A refined classification could provide a powerful tool individualize treatment regimes and identify individuals with increased risk of complications already at diagnosis.\n\nMethodsWe applied data-driven cluster analysis (k-means and hierarchical clustering) in newly diagnosed diabetic patients (N=8,980) from the Swedish ANDIS (All New Diabetics in Scania) cohort, using five variables (GAD-antibodies, BMI, HbA1c, HOMA2-B and HOMA2-IR), and related to prospective data on development of complications and prescription of medication from patient records. Replication was performed in three independent cohorts: the Scania Diabetes Registry (SDR, N=1466), ANDIU (All New Diabetics in Uppsala, N=844) and DIREVA (Diabetes Registry Vaasa, N=3485). Cox regression and logistic regression was used to compare time to medication, time to reaching the treatment goal and risk of diabetic complications and genetic associations.\n\nFindingsWe identified 5 replicable clusters of diabetes patients, with significantly different patient characteristics and risk of diabetic complications. Particularly, individuals in the most insulin-resistant cluster 3 had significantly higher risk of diabetic kidney disease, but had been prescribed similar diabetes treatment compared to the less susceptible individuals in clusters 4 and 5. The insulin deficient cluster 2 had the highest risk of retinopathy. In support of the clustering, genetic associations to the clusters differed from those seen in traditional T2D.\n\nInterpretationWe could stratify patients into five subgroups predicting disease progression and development of diabetic complications more precisely than the current classification. This new substratificationn may help to tailor and target early treatment to patients who would benefit most, thereby representing a first step towards precision medicine in diabetes.\n\nFundingThe funders of the study had no role in study design, data collection, analysis, interpretation or writing of the report.\n\nResearch in contextEvidence before this study\n\nThe current diabetes classification into T1D and T2D relies primarily on presence (T1D) or absence (T2D) of autoantibodies against pancreatic islet beta cell autoantigens and age at diagnosis (earlier for T1D). With this approach 75-85% of patients are classified as T2D. A third subgroup, Latent Autoimmune Diabetes in Adults (LADA,<10%), is defined by presence of autoantibodies against glutamate decarboxylase (GADA) with onset in adult age. In addition, several rare monogenic forms of diabetes have been described, including Maturity Onset Diabetes of the Young (MODY) and neonatal diabetes. This information is provided by national guidelines (ADA,WHO, IDF, Diabetes UK etc) but has not been much updated during the past 20 years and very few attempts have been made to explore heterogeneity of T2D. A topological analysis of potential T2D subgroups using electronic health records was published in 2015 but this information has not been implemented in the clinic.\n\nAdded value of this study\n\nHere we applied a data-driven cluster analysis of 5 simple variables measured at diagnosis in 4 independent cohorts of newly-diagnosed diabetic patients (N=14755) and identified 5 replicable clusters of diabetes patients, with significantly different patient characteristics and risk of diabetic complications. Particularly, individuals in the most insulin-resistant cluster 3 had significantly higher risk of diabetic kidney disease.\n\nImplications of the available evidence\n\nThis new sub-stratification may help to tailor and target early treatment to patients who would benefit most, thereby representing a first step towards precision medicine in diabetes

epidemiology↗