Biology subjects

Brinkmann, K.

Publications and source records attributed to Brinkmann, K..

4 recordsLinked to original sources

bioRxiv2023

Relative importance of MCL-1's Anti-Apoptotic versus Non-Apoptotic Functions in vivo

MCL-1 is an anti-apoptotic member of the BCL-2 protein family that ensures cell survival by blocking the intrinsic apoptotic cell death pathway1. MCL-1 is unique in being essential for early embryonic development and the survival of many cell types, including many cancer cells, which are not affected by the loss of the other anti-apoptotic BCL-2 family members1-4. Non-apoptotic functions of MCL-1 controlling mitochondrial ATP production and dynamics have been proposed to underlie this unique requirement for MCL-15-9. The relative contributions of the anti-apoptotic versus the non-apoptotic functions of MCL-1 in normal physiology have not been addressed. Here we replaced the coding sequence for MCL-1 with those for the anti-apoptotic proteins BCL-XL, BCL-2 or A1. We hypothesised that BCL-XL, BCL-2 and A1 may substitute for MCL-1 in the inhibition of apoptosis, but that they will not be able to replace MCL-1s non-apoptotic function. Strikingly, Mcl-1Bcl-xL/Bcl-xL and Mcl-1Bcl-2/Bcl-2 embryos survived to embryonic day 14.5, greatly surpassing the pre-implantation lethality of Mcl-1-/- embryos at E3.5. This demonstrates that the non-apoptotic functions of MCL-1 are dispensable for early development. However, at later stages of development and life after birth many cell types, particularly ones with high energy demand, were found to require both the anti-apoptotic and the non-apoptotic functions of MCL-1. These findings reveal the relative importance of these distinct functions of MCL-1 in physiology, providing important information for basic biology and the advancement of MCL-1 inhibitors in cancer therapy.

cell biology↗

bioRxiv2022

Combined absence of TRP53 target genes ZMAT3, PUMA and p21 cause a high incidence of cancer in mice

Transcriptional activation of target genes is essential for TP53-mediated tumour suppression, though the roles of many TP53-activated target genes in tumour suppression remains poorly understood. Knockdown of ZMAT3 in haematopoietic stem/progenitor cells by shRNA caused leukaemia only with the concomitant absence of the pro-apoptotic BCL-2 family member PUMA and the CDK inhibitor p21. We were interested to further investigate the role of ZMAT3 in tumour suppression beyond the haematopoietic system. Therefore, we generated Zmat3 knockout and compound gene knockout mice, lacking Zmat3 and p21, Zmat3 and Puma or all three genes. Puma-/-p21-/-Zmat3-/- triple knockout mice developed tumours at a significantly higher frequency compared to wild type, Puma-/-Zmat3-/- or p21-/- Zmat3-/-deficient mice. Interestingly, we observed that the triple and Puma-/-Zmat3-/- double deficient animals succumbed to lymphoma, while p21-/-Zmat3-/- animals developed mainly solid cancers. This analysis suggests that in addition to ZMAT3 loss, additional TRP53-regulated processes must be disabled simultaneously for TRP53-mediated tumour suppression to fail. Interestingly, our findings also reveal that the absence of different TRP53 regulated tumour suppressive processes changes the tumour spectrum, which suggests that different TRP53 tumour suppressive pathways are more critical in different tissues.

cancer biology↗

bioRxiv2020

BCL-XL is essential for the protection from secondary anemia caused by radiation-induced fatal kidney damage

Studies of gene-targeted mice identified the roles of the different pro-survival BCL-2 proteins during embryogenesis, but less is known about the roles of these proteins in adults, including in the response to cytotoxic stresses, such as treatment with anti-cancer agents. We investigated the role of BCL-XL in adult mice using a strategy where prior bone marrow transplantation allowed for loss of BCL-XL exclusively in non-hematopoietic tissues to prevent anemia caused by BCL-XL-deficiency in erythroid cells. Unexpectedly, the combination of total-body {gamma}-irradiation (TBI) and genetic loss of Bcl-x caused secondary anemia resulting from chronic renal failure due to apoptosis of renal tubular epithelium with secondary obstructive nephropathy. These findings identify a critical protective role of BCL-XL in the adult kidney and inform on the use of BCL-XL inhibitors in combinations with DNA damage-inducing drugs for cancer therapy. SummaryThe inducible loss of BCL-XL in all cells of adult mice causes primary anemia due to apoptosis of erythroid and megakaryocytic cell populations. In contrast {gamma}-radiation plus loss of BCL-XL in all cells except hematopoietic cells causes secondary anemia resulting from kidney damage.

pharmacology and toxicology↗

bioRxiv2018

miR17~92 is essential for the survival of hematopoietic stem and progenitor cells by restraining pro-apoptotic BIM

The micro RNA cluster miR17~92, also known as oncomiR-1, impacts diverse cellular processes, such as cell survival and proliferation. Constitutive loss of miR17~92 in mice causes severe defects in skeletal development, organ development and hematopoiesis, resulting in early post-natal lethality. The critical functions of miR17~92 in a fully developed animal have not yet been explored. Here we show that deletion of miR17~92 in adult mice [Formula] had no impact on their lifespan or general well-being. However, detailed analysis of the hematopoietic system in [Formula] mice, revealed a dramatic reduction in all mature hematopoietic lineages, which was due to the loss of early hematopoietic stem/progenitor cells (HSPCs). Strikingly, the concomitant loss of the pro-apoptotic BH3-only protein BIM rescued the loss of the HSPCs and all of their differentiated progeny that was caused by the deletion of miR17~92. These findings demonstrate that miR17~92 is critical for the survival of HSPCs by restraining the activity of the pro-apoptotic BH3-only protein BIM.

cell biology↗