Biology subjects

Zimyanin, V.

Publications and source records attributed to Zimyanin, V..

3 recordsLinked to original sources

bioRxiv2023

Live cell imaging of ATP levels reveals metabolic compartmentalization within motoneurons and early metabolic changes in FUS ALS motoneurons.

Motoneurons are one of the highest energy demanding cell types and a primary target in Amyotrophic lateral sclerosis (ALS), a debilitating and lethal neurodegenerative disorder without currently available effective treatments. Disruption of mitochondrial ultra-structure, transport and metabolism is a commonly reported phenotype in ALS models and can critically affect survival and proper function of motor neurons. However, how changes in metabolic rates contribute to ALS progression are not fully understood yet. Here we utilize hiPCS derived motoneuron cultures and live imaging quantitative techniques to evaluate metabolic rates in Fused in Sarcoma (FUS)-ALS model cells. We show that differentiation and maturation of motoneurons is accompanied by an overall upregulation of mitochondrial components and significant increase in metabolic rates that corresponds to their high energy-demanding state. Detailed compartment-specific live measurements using a fluorescent ATP sensor and FLIM imaging show significantly lower levels of ATP in the somas of cells carrying FUS-ALS mutations. These changes lead to the increased vulnerability of disease motoneurons to further metabolic challenges with mitochondrial inhibitors and could be due to the disruption of mitochondrial inner membrane integrity and an increase in its proton leakage. Furthermore, our measurements demonstrate heterogeneity between axonal and somatic compartments with lower relative levels of ATP in axons. Our observations strongly support the hypothesis that mutated FUS impacts metabolic states of motoneurons and makes them more susceptible to further neurodegenerative mechanisms.

neuroscience↗

bioRxiv2021

NDC1 is necessary for stable assembly of the nuclear pore scaffold to establish nuclear transport in early C. elegans embryos

Nuclear pore complexes (NPCs) are large protein assemblies that facilitate transport of macromolecules across the nuclear envelope (NE) [1, 2]. How thousands of NPCs rapidly assemble after open mitosis to form a functional NE is not known. Recruitment of the Nup107-160 outer ring scaffold to chromatin initiates NPC assembly. The Nup53/93 complex bridges the outer ring to the central channel to form a functional pore [3-6]. Nup53 interacts with the conserved transmembrane nucleoporin Ndc1; however, how Ndc1 contributes to post-mitotic NPC assembly is unclear [7-9]. Here, we use C. elegans embryos to show that the timely formation of a functional NE after mitosis depends on Ndc1. Endogenously tagged Ndc1 is recruited early to the reforming NE and is highly mobile in the nuclear rim. 3D analysis of post-mitotic NE formation revealed a decreased NPC density in NEs of ndc1 deleted embryos - continuous nuclear membranes contained few holes where assembling NPCs are normally located. Nup160 is highly mobile in NEs depleted of Ndc1 and outer ring scaffold components are less enriched at the rim. When both ndc1 and nup53 are absent, nuclear assembly fails. Together, these data show that Ndc1 dynamically associates with the NE and promotes stable association of the outer ring scaffold in the NE to facilitate NPC assembly after open mitosis. Furthermore, Ndc1 and Nup53 function in parallel to drive nuclear assembly. We propose that Ndc1 is a dynamic membrane adaptor that helps recruit and promote the self-assembly of the nuclear pore scaffold to drive post-mitotic NPC assembly.

cell biology↗

bioRxiv2021

The Drosophila anterior-posterior axis is polarized by asymmetric myosin activation

The Drosophila anterior-posterior (AP) axis is specified at mid-oogenesis when Par-1 kinase is recruited to the posterior cortex of the oocyte, where it polarises the microtubule cytoskeleton to define where the axis determinants, bicoid and oskar mRNAs localise. This polarity is established in response to an unknown signal from the follicle cells, but how this occurs is unclear. Here we show that the myosin chaperone, Unc-45 and Non-Muscle Myosin II (MyoII) are required in the germ line upstream of Par-1 in polarity establishment. Furthermore, the Myosin regulatory Light Chain (MRLC) is di-phosphorylated at the oocyte posterior in response to the follicle cell signal, inducing longer pulses of myosin contractility at the posterior and increased cortical tension. Over-expression of MRLC-T21A that cannot be di-phosphorylated or acute treatment with the Myosin light chain kinase inhibitor ML-7 abolish Par-1 localisation, indicating that posterior of MRLC di-phosphorylation is essential for polarity. Thus, asymmetric myosin activation polarizes the anterior-posterior axis by recruiting and maintaining Par-1 at the posterior cortex. This raises an intriguing parallel with AP axis formation in C. elegans where MyoII is also required to establish polarity, but functions to localize the anterior PAR proteins rather than PAR-1.

developmental biology↗