Biology subjects

Schmidt, J. H.

Publications and source records attributed to Schmidt, J. H..

5 recordsLinked to original sources

bioRxiv2025

A proteome-wide screen for membrane-interactions in intrinsically disordered regions of transmembrane proteins reveals a role in disease

Transmembrane proteins mediate essential cellular processes including signaling, transport, and ion flux. Besides their well-characterized structured domains, most contain intrinsically disordered regions, whose biological roles remain poorly understood. Evidence suggests that the functions of intrinsically disordered regions are context-dependent, a trait particularly relevant when anchored to cellular membranes. In this study, we probed peptide arrays with fluorescent liposomes to generate a high-resolution, proteome-wide map of membrane-interaction sites within intrinsically disordered regions of human transmembrane proteins. Screening 4,000 proteins, we identified membrane-interaction sites in [~]60% of cases. Among these, [~]63% represent amphipathic helices, while [~]17% resemble cationic cell-penetrating peptides. We demonstrate that membrane-interaction motifs can influence subcellular localization and may contribute to both physiological and pathological processes. Our findings establish membrane association as a key functional aspect of intrinsically disordered regions and provide a valuable resource for discovering non-canonical regulatory mechanisms in transmembrane proteins. The resource is available at MemRIDRdb.

cell biology↗

bioRxiv2024

BRAT1 - a new therapeutic target for glioblastoma

Glioblastoma (GBM), the most malignant primary brain tumor in adults, has poor prognosis irrespective of therapeutic advances due to its radio-resistance and infiltrative growth into brain tissue. The present study assessed functions and putative druggability of protein breast cancer type 1 susceptibility protein (BRCA1)-associated Ataxia telangiectasia mutated (ATM)-activator 1 (BRAT1) as a crucial factor driving key aspects of GBM, including enhanced DNA damage response and tumor migration. By a stable depletion of BRAT1 in GBM and glioma stem-like (GSC) cell lines, we observed a delay in DNA double-strand break repair and increased sensitivity to radiation treatment, corroborated by in vitro and in vivo studies demonstrating impaired tumor growth and invasion. Proteomic analyses further emphasize the role of BRAT1s cell migration and invasion capacity, with a notable proportion of downregulated proteins associated with these processes. In line with the genetic manipulation, we found that treatment with the BRAT1 inhibitor Curcusone D (CurD) significantly reduced GSC migration and invasion in an ex vivo slice culture model, particularly when combined with irradiation, resulting a synergistic inhibition of tumor growth and infiltration. Our results reveal that BRAT1 contributes to GBM growth and invasion and suggest that therapeutic inhibition of BRAT1 with CurD or similar compounds might constitute a novel approach for anti-GBM directed treatments.

cancer biology↗

bioRxiv2024

Membrane curvature association of amphipathic helix 8 drives constitutive GPCR endocytosis

Cellular signaling relies on the activity of transmembrane receptors and their presentation on the cellular surface. Their continuous insertion in the plasma membrane is balanced by constitutive and activity dependent internalization, which is orchestrated by adaptor proteins recognizing semi-specific motifs within the receptors intracellular regions. Here we describe a complementary and evolutionary conserved and refined trafficking mechanism for G-protein coupled receptors (GPCR). This mechanism relies on the insertion of their amphipathic helix 8 into the inner leaflet of lipid membranes, orthogonal to the transmembrane helices. These amphipathic helices dictate subcellular localization of the receptors and autonomously drive their endocytosis by cooperative assembly and association with areas of high membrane curvature. The strength of helix 8 membrane insertion propensity quantitatively predicts the rate of constitutive internalization of GPCRs. This discovery advances our understanding of membrane protein trafficking and highlights a new principle of receptor-lipid interactions that may have broader implications for cellular signaling and therapeutic targeting. One-Sentence SummaryReceptor proteins navigate cellular membranes by interacting with their curvature using an evolutionary conserved mechanism that relies on amphipathic helices and complements direct coupling to the endocytic protein machinery.

cell biology↗

bioRxiv2020

Coding variants identified in diabetic patients alter PICK1 BAR domain function in insulin granule biogenesis

Bin/amphiphysin/Rvs (BAR) domains are positively charged crescent-shaped modules that shape negatively charged curved lipid membranes during membrane remodeling processes. The BAR domain proteins ICA69, PICK1 and arfaptins have recently been demonstrated to coordinate the budding and formation of immature secretory granules (ISGs) at the trans-Golgi network. Here, we identify four coding variants in the PICK1 gene from a Danish whole-exome screening of diabetic patients, that all involve change of positively charged residues in the PICK1 BAR domain. All four coding variants failed to rescue the insulin content in INS-1E cells upon KD of endogenous PICK1. Moreover, two variants showed dominant negative properties. Interestingly, in vitro assays addressing the BAR domain function suggest that the coding variants compromised membrane binding capacity but increased capacity to cause fission of liposomes. Live confocal microscopy and super-resolution microscopy further revealed that PICK1 resides transiently on ISGs before egress via vesicular budding events. Interestingly, this egress of PICK1 was accelerated in the coding variants. We propose that PICK1 assists or complements the removal of excess membrane and generic membrane trafficking proteins, and possibly also insulin from ISGs during the maturation process and that the coding variants may cause premature budding possibly explaining their dominant negative function.

cell biology↗

bioRxiv2020

Bacterivorous nematodes correlate with soil fertility and improved crop production in an organic minimum tillage system

Organic farming systems are generally based on intensive soil tillage for seed bed preparation and weed control, which in the long-term often leads to reduced soil fertility. To avoid this, organic farming systems need to adopt conservation agriculture practices, such as minimum tillage and diligent crop rotations. However, minimum tillage generally delays soil warming in spring causing reduced nitrogen mineralization and thus poor plant growth. This negative effect needs to be compensated. We hypothesize that, in a diverse crop rotation, organic minimum tillage based on frequent cover cropping and application of dead mulch will improve soil fertility and thus crop production as confirmed by a number of chemical and biological soil indicators. We made use of two long-term field experiments that compare typical organic plough-based systems (25 cm) with minimum tillage systems (<15 cm) including application of transfer mulch to potatoes. Both tillage systems were either fertilized with compost or equivalent amounts of mineral potassium and phosphate. In 2019, soil samples from both fields were collected and analyzed for soil pH, organic carbon, macro-, micronutrients, microbial biomass, microbial activity and total nematode abundance. In addition, performance of pea in the same soils was determined under greenhouse conditions. Results from the field experiments showed an increase of macronutrients (+52%), micronutrients (+11%), microbial biomass (+51%), microbial activity (+86%), and bacterivorous nematodes (+112%) in minimum tillage compared with the plough-based system. In the accompanying greenhouse bioassay, pea biomass was 45% higher under minimum than under plough tillage. In conclusion, the study showed that under organic conditions, soil fertility can be improved in minimum tillage systems by intensive cover cropping and application of dead mulch to levels higher than in a plough-based system. Furthermore, the abundance of bacterivorous nematodes can be used as a reliable indicator for the soil fertility status.

ecology↗