Biology subjects

Hassdenteufel, S.

Publications and source records attributed to Hassdenteufel, S..

3 recordsLinked to original sources

bioRxiv2025

A multiplexed approach for genetic screening of human cells by electron microscopy uncovers a critical effector of mitochondrial cristae shape

Mitochondria form complex and diverse membrane-architectures essential for their multiple functions. Whereas critical proteins sculpting mitochondrial membranes have been identified, the molecular basis for many key features remains enigmatic. Exploration of membrane ultrastructure, in general, is limited by the tradeoff between resolution and throughput: electron microscopy (EM) is essential to resolve their ultrastructure but lacks scalability for systematic functional discovery. To overcome this limitation, we developed a high-resolution screening pipeline for EM of multiplexed human cell pools, hMultiCLEM (human Multiplexed Correlative Light and EM). To showcase the power of hMultiCLEM we performed a genetic screen exploring mitochondrial ultrastructure. hMultiCLEM confirmed proposed cristae modulators and uncovered additional ones illuminating the protein networks driving cristae organization. Validation of candidates highlighted an intermembrane space (IMS) protein linked to Menieres disease, which we named MISHA (Mitochondrial-IMS membrane-SHApe-impacting protein). More broadly, hMultiCLEM transforms the EM field, enabling genetic/chemical screening in basic and medical research.

cell biology↗

bioRxiv2024

Mitochondrial inner membrane remodeling as a driving force of organelle shaping

Mitochondria are dynamic organelles exhibiting diverse shapes. While the variation of shapes, ranging from spheres to elongated tubules, and the transition between them, are clearly seen in many cell types, the molecular mechanisms governing this morphological variability remain poorly understood. Here, we propose a novel shaping mechanism based on the interplay between the inner and outer mitochondrial membranes. Our biophysical model suggests that the difference in surface area, arising from the pulling of the inner membrane into cristae, correlates with mitochondrial elongation. Analysis of live cell super-resolution microscopy data supports this correlation, linking elongated shapes to the extent of cristae in the inner membrane. Knocking down cristae shaping proteins further confirms the impact on mitochondrial shape, demonstrating that defects in cristae formation correlate with mitochondrial sphericity. Our results suggest that the dynamics of the inner mitochondrial membrane are important not only for simply creating surface area required for respiratory capacity, but go beyond that to affect the whole organelle morphology. This work explores the biophysical foundations of individual mitochondrial shape, suggesting potential links between mitochondrial structure and function. This should be of profound significance, particularly in the context of disrupted cristae shaping proteins and their implications in mitochondrial diseases.

cell biology↗

bioRxiv2019

Proteomics identifies signal peptide features determining the substrate specificity in human Sec62/Sec63-dependent ER protein import

In mammalian cells one-third of all polypeptides are integrated into the membrane or translocated into the lumen of the endoplasmic reticulum (ER) via the Sec61-channel. While the Sec61-complex facilitates ER-import of most precursor polypeptides, the Sec61-associated Sec62/Sec63-complex supports ER-import in a substrate-specific manner. So far, mainly posttranslationally imported precursors and the two cotranslationally imported precursors of ERj3 and prion protein were found to depend on the Sec62/Sec63-complex in vitro. Therefore, we determined the rules for engagement of Sec62/Sec63 in ER-import in intact human cells using a recently established unbiased proteomics approach. In addition to confirming ERj3, we identified twenty-two novel Sec62/Sec63-substrates under these in vivo-like conditions. As a common feature, those previously unknown substrates share signal peptides with comparatively longer but less hydrophobic H-region and lower C-region polarity. Further analyses with four substrates, and ERj3 in particular, revealed the combination of a slowly-gating signal peptide and a downstream translocation-disruptive positively charged cluster of amino acid residues as decisive for the Sec62-/Sec63-requirement. In the case of ERj3, these features were found to be responsible for an additional BiP-requirement and to correlate with sensitivity towards the Sec61-channel inhibitor CAM741. Thus, the human Sec62/Sec63-complex may support Sec61-channel opening for precursor polypeptides with slowly-gating signal peptides by direct interaction with the cytosolic amino-terminal peptide of Sec61 or via recruitment of BiP and its interaction with the ER-lumenal loop 7 of Sec61. These novel insights into the mechanism of human ER protein import contribute to our understanding of the etiology of SEC63-linked Polycystic Liver Disease. DatabasesThe mass spectrometry proteomics data have been deposited to the ProteomeXchange Consortium via the PRIDE partner repository (http://www.ebi.ac.uk/pride/archive/projects/Identifiers) with the dataset identifiers: PXD008178, PXD011993, and PXD012078. Supplementary information was deposited at Mendeley Data under the DOI:10.17632/6s5hn73jcv.1 (http://dx.doi.or/10.17632/6s5hn73jcv.1).

biochemistry↗