Biology subjects

Hoehne, M.

Publications and source records attributed to Hoehne, M..

7 recordsLinked to original sources

bioRxiv2024

SusC/D-like proteins in Gammaproteobacteria that utilize fructans

Fructans are ubiquitous in terrestrial ecosystems, however, these glycans are unexplored in the marine environment. We have discovered that the Antarctic gammaproteobacterium Pseudoalteromonas distincta is highly adapted to the degradation of fructose-containing substrates. This is enabled by proteins encoded in several genomic regions, including a fructan polysaccharide utilization locus (PUL). In addition to a glycoside hydrolase from family 32 (GH32), the fructan PUL encodes two proteins that have been described as specific for Bacteroidota and were previously unknown for Gammaproteobacteria: a glycan-binding SusD-like protein and a SusC-like TonB-dependent transporter (TBDT), which work as a complex in glycan import. Proteome analyses and biochemistry results suggest that the SusC/D-like proteins of P. distincta shuttle small-sized inulin-type fructans directly into the cell, where they are degraded by a periplasmic exo-active GH32. A SusD-like protein could provide a competitive adavantage in the absence of extracelluar endo-active inulinases. Comparative genomics identified further SusC/D-like proteins in Gammaproteobacteria, most of which are co-encoded with GH32s, indicative of fructan PULs, and are frequently associated with the marine habitat. Our study thus shows the first known exception to the paradigm that only Bacteroidota use SusC/D-like proteins. It further suggests that fructans contribute to the marine glycan pool.

molecular biology↗

bioRxiv2023

Mechanical forces at the kidney filtration barrier govern spatial orientation of podocyte processes on capillaries

Mammalian kidneys filter enormous volumes of water and small solutes, a filtration driven by the very high hydrostatic pressure in glomerular capillaries. Interdigitating cellular processes of podocytes form the slits for fluid filtration. They are connected by the membrane-like slit diaphragm cell junction containing a mechanosensitive ion channel complex and allow filtration while counteracting hydrostatic pressure. Using high-resolution microscopy, we show that filtration-slit-generating secondary processes preferentially align along the capillaries longitudinal axis while primary processes are preferably perpendicular to the longitudinal direction. The preferential orientation requires maturation in development and is lost in disease states. We demonstrate that loss of proper orientation might contribute to impaired filtration by collapsing of the filtration slits and reducing the mechanical stability of podocyte processes. Together, these data suggest that podocytes sense mechanical strain to utilize circumferential hoop stress balancing the massive mechanical strain generated from fluid flow over the filtration slit.

cell biology↗

bioRxiv2021

Three-dimensional Super-resolved Imaging of Paraffin-embedded Kidney Samples

Diseases of the glomeruli, the renal filtration units, are a leading cause of progressive kidney disease. Assessment of the ultrastructure of podocytes at the glomerular filtration barrier is essential for diagnosing diverse disease entities, providing insight into the disease pathogenesis as well as monitoring treatment responses. New technologies, including superresolved nanoscopy and expansion microscopy, as well as new sample preparation techniques, are starting to revolutionize imaging of biopsy specimens. However, our previous approaches for simple and fast three-dimensional imaging of optically cleared samples are to date not compatible with formalin fixed paraffin-embedded (FFPE) tissue, impeding application in clinical routine. Here we provide protocols that circumvent these limitations and allow for three dimensional STED and confocal imaging of FFPE kidney tissue with similar staining and image quality as compared to our previous approaches. This would increase the feasibility to implement these protocols in clinical routines, as FFPE is the gold standard method for storage of patient samples.

pathology↗

bioRxiv2021

Organ protection by caloric restriction depends on activation of the de novo NAD+ synthesis pathway

Therapeutic strategies to treat acute kidney injury (AKI) are lacking in clinical practice. Interestingly, preconditioning by hypoxia (HP) and caloric restriction (CR) is highly protective in rodent AKI models. However, the underlying molecular mechanisms of this process are unknown. A comparative transcriptome analysis of murine kidneys after HP and CR identified Kynureninase (KYNU) as a common downstream target. Using a newly generated KYNU-deficient mouse line, we show that KYNU strongly contributes to the protective effect of preconditioning. Metabolome, transcriptome and proteome analyses reveal the KYNU-dependent de novo nicotinamide adenine dinucleotide (NAD+) biosynthesis pathway as necessary for CR-associated maintenance of NAD+ levels. Importantly, the impact of CR on the de novo NAD+ biosynthesis pathway can be recapitulated in humans. These findings provide a valuable insight into the molecular mechanisms mediating protection upon preconditioning and point towards the de novo branch of NAD+ biosynthesis as a conserved target in nephroprotection.

physiology↗

bioRxiv2021

Deep learning-based segmentation and quantification of podocyte foot process morphology

The kidneys constantly filter enormous amounts of fluid, with almost complete retention of albumin and other macromolecules in the plasma. Diseases of podocytes at the kidney filtration barrier reduce the intrinsic permeability of the capillary wall resulting in albuminuria. However, direct quantitative assessment of the underlying morphological changes has previously not been possible. Here we developed a deep learning-based approach for segmentation of foot processes in images acquired with optical microscopy. Our method - Automatic Morphological Analysis of Podocytes (AMAP) - accurately segments foot processes and robustly quantifies their morphology. It also robustly determined morphometric parameters, at a Pearson correlation of r > 0.71 with a previously published semi-automated approach, across a large set of mouse tissue samples. The artificial intelligence algorithm wasWe applied the analysis to a set of human kidney disease conditions allowing comprehensive quantification of various underlying morphometric parameters. These results confirmed that when podocytes are injured, they take on a more simplified architecture and the slit diaphragm length is significantly shortened, resulting in a reduction in the filtration slit area and a loss of the buttress force of podocytes which increases the permeability of the glomerular basement membrane to albumin.

pathology↗

bioRxiv2020

Par3A and Par3B orchestrate podocyte architecture by regulating RhoA levels

Glomerular diseases are a major cause for chronic kidney disorders. In the majority of cases podocyte injury is causative for disease development. Cytoskeletal rearrangements and morphological changes are hallmark features of podocyte injury and result in dedifferentiation and subsequent loss of podocytes. Here, we establish a link between components of the Par3 polarity complex and actin regulators, which are necessary to establish and maintain the podocytes architecture utilizing both, mouse and Drosophila models. We demonstrate that the two mammalian Par3 proteins, Par3A and Par3B, share redundant functions despite differing in their ability to interact with other components of the Par complex. Only simultaneous inactivation of both Par3 proteins causes a severe disease phenotype in mouse podocytes by regulating Rho-GTP levels involving the actin regulators Synaptopodin and CD2AP in an aPKC independent manner.

cell biology↗

bioRxiv2017

Individual nephron proteomes connect morphology and function in proteinuric kidney disease

In diseases of many parenchymatous organs, heterogenous detoriation of individual functional units determines the clinical prognosis. However, the molecular characterization of these subunits remains a technological challenge that needs to be addressed in order to better understand pathological mechanisms. Sclerotic and proteinuric glomerular kidney disease is a frequent and heterogeneous disease which affects a fraction of nephrons, glomeruli and draining tubules, to variable extents, and for which no treatment exists. Here, we developed and applied an antibody-independent methodology to investigate heterogeneity of individual nephron segment proteomes from mice with proteinuric kidney disease. This \"one-segment-one-proteome-approach\" defines mechanistic connections between upstream (glomerular) and downstream (tubular) nephron segment populations. In single glomeruli from two different mouse models of sclerotic glomerular disease, we identified a coherent protein expression module consisting of extracellular matrix protein deposition (reflecting glomerular sclerosis), glomerular albumin (reflecting proteinuria) and LAMP1, a lysosomal protein. This module was associated with a loss of podocyte marker proteins. In an attempt to target this protein co-expression module, genetic ablation of LAMP1-correlated lysosomal proteases in mice could ameliorate glomerular damage. Furthermore, individual glomeruli from patients with genetic sclerotic and non-sclerotic proteinuric diseases demonstrated increased abundance of lysosomal proteins, in combination with a decreased abundance of the mutated gene products. Therefore, increased glomerular lysosomal load is a conserved key mechanism in proteinuric kidney diseases, and the technology applied here can be implemented to address heterogeneous pathophysiology in a variety of diseases at a sub-biopsy scale

physiology↗