Biology subjects

Lorenz, S.

Publications and source records attributed to Lorenz, S..

4 recordsLinked to original sources

bioRxiv2018

Induction of the BIMS Splice Variant Sensitizes Proliferating NK Cells to IL-15 Withdrawal

Adoptive transfer of allogeneic NK cells holds great promise for cancer immunotherapy. There is a variety of protocols to expand NK cells in vitro, most of which are based on stimulation with cytokines alone or in combination with feeder cells. Although IL-15 is essential for NK cell homeostasis in vivo, it is commonly used at supra-physiological levels to induce NK cell proliferation in vitro. As a result, adoptive transfer of such IL-15 addicted NK cells is associated with cellular stress due to sudden cytokine withdrawal. Here, we describe a dose-dependent addiction to IL-15 during in vitro expansion, leading to caspase-3 activation and profound cell death upon IL-15 withdrawal. NK cell addiction to IL-15 was tightly linked to the BCL-2/BIM ratio, which rapidly dropped during IL-15 withdrawal. Furthermore, we observed a proliferation-dependent induction of BIM short (BIM S), a highly pro-apoptotic splice variant of BIM, in IL-15 activated NK cells. These findings shed new light on the molecular mechanisms involved in NK cell apoptosis following cytokine withdrawal and may guide future NK cell priming strategies in a cell therapy setting.

immunology↗

bioRxiv2018

TRPML1-mediated Modulation of Dense-core Granules Tunes Functional Potential in NK Cells

Inhibitory signaling during natural killer (NK) cell education translates into increased responsiveness to activation; however the intracellular mechanism for functional tuning by inhibitory receptors remains unclear. We found that educated NK cells expressing self-MHC specific inhibitory killer cell immunoglobulin-like receptors (KIR) show accumulation of granzyme B, localized in dense-core secretory lysosomes, converged close to the centrosome. This discrete morphological phenotype persists in self-KIR+ NK cells independently of transcriptional programs that regulate effector function, metabolism and lysosomal biogenesis. The granzymeB dense, large secretory lysosomes in self-KIR+ NK cells were efficiently released upon target cell recognition, contributing to their enhanced cytotoxic capacity. Secretory lysosomes are part of the acidic lysosomal compartment, which has been shown to channel calcium and mediate intracellular signalling in several cell types. Interference of signaling from acidic Ca2+ stores in primary NK cells reduced both target-specific Ca2+-flux, degranulation and cytokine production. Furthermore, inhibition of PI(3,5)P2 synthesis or genetic silencing of the PI(3,5)P2-regulated lysosomal Ca2+-channel TRPML1 led to increased levels of granzyme B and enhanced functional potential. These results indicate an intrinsic role for lysosomal homeostasis in NK cell education.

immunology↗

bioRxiv2017

Sample-Index Misassignment Impacts Tumor Exome Sequencing

Sample pooling enabled by dedicated indexes is a common and cost-effective strategy used in high-throughput DNA sequencing. Index misassignment leading to cross-sample contamination has however been described as a general problem of sequencing instruments which utilize exclusion amplification. Using real-life data from multiple tumor sequencing projects, we demonstrate that co-multiplexed samples can induce artifactual calls closely resembling high-quality somatic variant calls, and argue that dual indexing is the most reliable countermeasure.

genomics↗

bioRxiv2017

The phosphatase PTPRG controls FGFR1 activity and influences sensitivity to FGFR kinase inhibitors

FGFR1 represents an important target for precision medicine and a detailed molecular understanding of the target is important in order to increase the efficacy of FGFR inhibitors. We have here applied proximity labelling of FGFR1 in an osteosarcoma cell line to identify determinants of FGFR1 activity. Many known FGFR interactors were identified (e.g. FRS2, PLC{gamma}, RSK2, SHC4, SRC), but the data also suggested novel determinants. A strong hit in our screen was the tyrosine phosphatase PTPRG. We show that PTPRG and FGFR1 interact and colocalize at the plasma membrane where PTPRG directly dephosphorylates activated FGFR1. We further show that osteosarcoma cell lines depleted for PTPRG display increased FGFR activity and are hypersensitive to stimulation by FGF1. In addition, PTPRG depletion elevated cell growth and negatively affected the efficacy of FGFR kinase inhibitors. Thus, PTPRG may have future clinical relevance by being a predictor of outcome after FGFR inhibitor treatment.

cell biology↗