Biology subjects

Grune, T.

Publications and source records attributed to Grune, T..

3 recordsLinked to original sources

bioRxiv2026

The primary cilium controls programmed cell death via its proteasome-regulating function

Primary cilia are tiny cellular protrusions of nearly every vertebrate cell controlling multiple cellular processes, such as proliferation, differentiation, migration etc. Their dysfunction results in severe human diseases collectively referred to as ciliopathies. Remarkably, many ciliopathies are associated with increased programmed cell death (PCD). However, it is largely unknown how primary cilia regulate PCD. In in vitro (murine and human cells) and in vivo (Xenopus laevis and mouse) models, we observed elevated PCD in the absence of the ciliopathy protein RPGRIP1L. Mechanistically, our data elucidated that RPGRIP1L controls PCD by governing the activity of the ciliary proteasome. By using super-resolution microscopy, we first showed that the apoptosis inducer MOAP1 localises to primary cilia. Furthermore, our investigations revealed that RPGRIP1L controls PCD via the degradation of MOAP1 by the ciliary proteasome. Based on our finding that two more ciliopathy proteins, TCTN1 and CEP290, modulate PCD via regulating the activity of the ciliary proteasome, we suggest that the proteasomal degradation of MOAP1 represents a general mechanism by which primary cilia control PCD.

cell biology↗

bioRxiv2024

A novel and robust method for assessing mitochondrial (dys)function in healthy and diseased frozen cardiac tissue

Cardiovascular diseases are often associated with impairment in mitochondrial function detected by reduced mitochondrial oxygen consumption using high-resolution respirometry. However, existing respirometry protocols are limited by the necessity for fresh tissue samples. This study developed a method with tailored substrate-inhibitor titration (TSIT) of mitochondrial electron transport complexes (ETC) to measure mitochondrial function in frozen cardiac samples using high-resolution respirometry. Briefly, acetyl-CoA was added to fuel the tricarboxylic acid (TCA) cycle for NADH production, enabling complex I (CI)-linked respiratory assessment. NADH was then added to measure maximum CI-linked respiratory capacity, followed by rotenone and succinate to assess complex II (CII)-linked respiratory capacity. TSIT detected mitochondrial functional differences between frozen atrial and ventricular tissue, with comparable results as measured in fresh samples. It also detected cardiac mitochondrial dysfunction across various (patho)physiological mouse models (including aging, ischemia reperfusion, obesity, and CI deficiency) as well as in frozen human donor samples, highlighting its clinical potential. Furthermore, we showed the first evidence for supercomplexes (SCs) formation between ETC-SCs and the TCA cycle metabolon, underpinning TSIT feasibility. In conclusion, we established a novel, robust, sensitive and translational method (TSIT) for assessing mitochondrial (dys)function in frozen cardiac samples from various species, enabling flexible analysis of mitochondrial function in both laboratory and clinical settings.

physiology↗

bioRxiv2024

Age pigment lipofuscin causes oxidative stress, lysosomal dysfunction, and pyroptotic cell death

Accumulation of the age pigment lipofuscin represents a ubiquitous hallmark of the aging process. However, our knowledge about cellular effects of lipofuscin accumulation is potentially flawed, because previous research mainly utilized highly artificial methods of lipofuscin generation. In order to address this tremendous problem, we developed a convenient protocol for isolation of authentic lipofuscin from human and equine cardiac tissue in high purity and quantity. Isolated lipofuscin aggregates contained elevated concentrations of proline and metals such as calcium or iron. The material was readily incorporated by fibroblasts and caused cell death at low concentrations (LC50 = 5.0 {micro}g/mL) via a pyroptosis-like pathway. Lipofuscin boosted mitochondrial ROS production and caused lysosomal dysfunction by lysosomal membrane permeabilization leading to reduced lysosome quantity and impaired cathepsin D activity. In conclusion, this is the first study utilizing authentic lipofuscin to experimentally validate the concept of the lysosomal-mitochondrial axis theory of aging and cell death.

cell biology↗