Biology subjects

Damme, M.

Publications and source records attributed to Damme, M..

5 recordsLinked to original sources

bioRxiv2021

The solute carrier MFSD1 decreases β1 integrins activation status and thus tumor metastasis

Solute carriers are increasingly recognized as participating in a plethora of pathologies, including cancer. We describe here the involvement of the orphan solute carrier MFSD1 in the regulation of tumor cell migration. Loss of MFSD1 enabled higher levels of metastasis in a mouse model. We identified an increased migratory potential in MFSD1-/- tumor cells which was mediated by increased focal adhesion turn-over, reduced stability of mature inactive {beta}1 integrin, and the resulting increased integrin activation index. We show that MFSD1 promoted recycling to the cell surface of endocytosed inactive {beta}1 integrin and thereby protected {beta}1 integrin from proteolytic degradation; this led to dampening of the integrin activation index. Furthermore, down-regulation of MFSD1 expression was observed during early steps of tumorigenesis and higher MFSD1 expression levels correlate with a better cancer patient prognosis. In sum, we describe a requirement for endolysosomal MFSD1 in efficient {beta}1 integrin recycling to suppress tumor spread.

cancer biology↗

bioRxiv2021

Ligands binding to the cellular prion protein induce its protective proteolytic release with therapeutic potential in neurodegenerative proteinopathies

The cellular prion protein (PrPC) is a central player in neurodegenerative diseases caused by protein misfolding, such as prion diseases or Alzheimers disease (AD). Expression levels of this GPI-anchored glycoprotein, especially at the neuronal cell surface, critically correlate with various pathomechanistic aspects underlying these diseases, such as templated misfolding (in prion diseases) and neurotoxicity and, hence, with disease progression and severity. In stark contrast to cell-associated PrPC, soluble extracellular forms or fragments of PrP are linked with neuroprotective effects, which is likely due to their ability to interfere with neurotoxic disease-associated protein conformers in the interstitial fluid. Fittingly, the endogenous proteolytic release of PrPC by the metalloprotease ADAM10 ( shedding) was characterized as a protective mechanism. Here, using a recently generated cleavage-site specific antibody, we shed new light on earlier studies by demonstrating that shed PrP (sPrP) negatively correlates with conformational conversion (in prion disease) and is markedly redistributed in murine brain in the presence of prion deposits or AD-associated amyloid plaques indicating a blocking and sequestrating activity. Importantly, we reveal that administration of certain PrP-directed antibodies and other ligands results in increased PrP shedding in cells and organotypic brain slice cultures. We also provide mechanistic and structural insight into this shedding-stimulating effect. In addition, we identified a striking exception to this, as one particular neuroprotective antibody, due to its special binding characteristics, did not cause increased shedding but rather strong surface clustering followed by fast endocytosis and degradation of PrPC. Both mechanisms may contribute to the beneficial action described for some PrP-directed antibodies/ligands and pave the way for new therapeutic strategies against devastating and currently incurable neurodegenerative diseases.

neuroscience↗

bioRxiv2021

AMPylation is a specific lysosomal protein posttranslational modification in neuronal maturation.

Protein AMPylation is a pervasive posttranslational modification with an emerging role in neurodevelopment. In metazoans the two highly conserved protein AMP-transferases together with a diverse group of AMPylated proteins have been identified using chemical proteomics and biochemical techniques. However, the function of this modification remains largely unknown. Particularly problematic is the localization of thus far identified AMPylated proteins and putative AMP-transferases. Here, we uncover protein AMPylation as a novel posttranslational modification of luminal lysosomal proteins characteristic in differentiating neurons. Through a combination of chemical proteomics, advanced gel-based separation of modified and unmodified proteins and activity assay, we show that an AMPylated, lysosomal soluble form of exonuclease PLD3 increases dramatically during neuronal maturation and that AMPylation inhibits its catalytic activity. Together, our findings unveil so far unknown lysosomal posttranslational modification, its connection to neuronal differentiation and putatively provide a novel molecular rationale to design of therapeutics for lysosomal storage diseases.

biochemistry↗

bioRxiv2021

LAMP3 is critical for surfactant homeostasis in mice

Lysosome-associated membrane glycoprotein 3 (LAMP3) is a type I transmembrane protein of the LAMP protein family with a cell-type-specific expression in alveolar type II cells in mice and hitherto unknown function. In type II pneumocytes, LAMP3 is localized in lamellar bodies, secretory organelles releasing pulmonary surfactant into the extracellular space to lower surface tension at the air/liquid interface. The physiological function of LAMP3, however, remains enigmatic. We generated Lamp3 knockout mice by CRISPR/Cas9. LAMP3 deficient mice are viable with an average life span and display regular lung function under basal conditions. The levels of a major hydrophobic protein component of pulmonary surfactant, SP-C, are strongly increased in the lung of Lamp3 knockout mice, and the lipid composition of the bronchoalveolar lavage shows mild but significant changes, resulting in alterations in surfactant functionality. In ovalbumin-induced experimental allergic asthma, the changes in lipid composition are aggravated, and LAMP3-deficient mice exert an increased airway resistance. Our data suggest a critical role of LAMP3 in the regulation of pulmonary surfactant homeostasis and normal lung function.

biochemistry↗

bioRxiv2020

Multi cell line analysis of lysosomal proteomes reveals unique features and novel lysosomal proteins

Lysosomes play a key role in the regulation of cellular metabolism and are increasingly recognized as highly active and diverse organelles which are involved in a large variety of processes. Their essential role is exemplified by the detrimental consequences of lysosomal malfunction, which can result in lysosomal storage disorders, neurodegenerative diseases, and cancer. Using lysosome enrichment and mass spectrometry, we investigated the lysosomal proteomes of six common cell lines. We provide first evidence for cell-type specific differences of lysosomes on a large scale, showing highly variable levels of distinct lysosomal proteins within one cell type, while others are highly conserved among cell lines. Using stable isotope labelling and bimodal distribution analysis, we identify high confidence lysosomal proteins for each cell line. Multi cell line correlation of these data reveals potential novel lysosomal proteins, and we confirm lysosomal localization for five candidates. All data are available via ProteomeXchange with identifier PXD020600.

molecular biology↗