Biology subjects

Rizwan, J.

Publications and source records attributed to Rizwan, J..

3 recordsLinked to original sources

bioRxiv2024

EDC-3 and EDC-4 Regulate Embryonic mRNA Clearance and Biomolecular Condensate Specialization

Animal development is dictated by the selective and timely decay of mRNAs in developmental transitions, but the impact of mRNA decapping scaffold proteins in development is unknown. This study unveils the roles and interactions of the DCAP-2 decapping scaffolds EDC-3 and EDC-4 in the embryonic development of C. elegans. EDC-3 facilitates the timely removal of specific embryonic mRNAs, including cgh-1, car-1, and ifet-1 by reducing their expression, and preventing excessive accumulation of DCAP-2 condensates in somatic cells. We further uncover a novel role for EDC-3 in defining the boundaries between P-bodies, germ granules, and stress granules. Lastly, we show that EDC-4 counteracts EDC-3 and engenders the assembly of DCAP-2 with the GID (CTLH) complex, a ubiquitin ligase involved in maternal-to-zygotic transition (MZT). Our findings support a model wherein multiple RNA decay mechanisms temporally partake in the clearance of maternal and zygotic mRNAs throughout embryonic development.

molecular biology↗

bioRxiv2023

Impact of histone deacetylase inhibition and arimoclomol on heat shock protein expression and disease biomarkers in primary culture models of familial ALS

Protein misfolding and mislocalization are common themes in neurodegenerative disorders, including the motor neuron disease, amyotrophic lateral sclerosis (ALS). Maintaining proteostasis is a crosscutting therapeutic target, including upregulation of heat shock proteins (HSP) to increase chaperoning capacity. Motor neurons have a high threshold for upregulating stress inducible HSPA1A, but constitutively express high levels of HSPA8. This study compared expression of these HSPs in cultured motor neurons expressing three variants linked to familial ALS: TDP-43G348C, FUSR521G or SOD1G93A. All variants were poor inducers of Hspa1a, and reduced levels of Hspa8 mRNA and protein, indicating multiple compromises in chaperoning capacity. To promote HSP expression, cultures were treated with the putative HSP co-inducer, arimoclomol, class I histone deacetylase (HDAC) inhibitors to promote active chromatin for transcription, and the combination. Treatments had variable, often different effects on expression of Hspa1a and Hspa8, depending on the ALS variant expressed, mRNA distribution (somata and dendrites), and biomarker of toxicity measured (histone acetylation, maintaining nuclear TDP-43 and the nBAF chromatin remodeling complex component Brg1, mitochondrial transport, FUS aggregation). Overall, HDAC inhibition alone was effective on more measures than arimoclomol. In the TDP-43 model, arimoclomol failed to induce HSPA1A or preserve Hspa8 mRNA, despite preserving nuclear TDP-43 and Brg1, indicating neuroprotective properties other than HSP induction. The data speak to the complexity of drug mechanisms against multiple biomarkers of ALS pathogenesis, as well as to the importance of HSPA8 for neuronal proteostasis in both somata and dendrites.

neuroscience↗

bioRxiv2023

Localized synthesis of molecular chaperones sustains neuronal proteostasis

Proteostasis is maintained through regulated protein synthesis and degradation and chaperone-assisted protein folding. However, this is challenging in neuronal projections because of their polarized morphology and constant synaptic proteome remodeling. Using high-resolution fluorescence microscopy, we discovered that hippocampal and spinal cord motor neurons of mouse and human origin localize a subset of chaperone mRNAs to their dendrites and use microtubule-based transport to increase this asymmetric localization following proteotoxic stress. The most abundant dendritic chaperone mRNA encodes a constitutive heat shock protein 70 family member (HSPA8). Proteotoxic stress also enhanced HSPA8 mRNA translation efficiency in dendrites. Stress-mediated HSPA8 mRNA localization to the dendrites was impaired by depleting fused in sarcoma--an amyotrophic lateral sclerosis-related protein--in cultured spinal cord mouse motor neurons or by expressing a pathogenic variant of heterogenous nuclear ribonucleoprotein A2/B1 in neurons derived from human induced pluripotent stem cells. These results reveal a crucial and unexpected neuronal stress response in which RNA-binding proteins increase the dendritic localization of HSPA8 mRNA to maintain proteostasis and prevent neurodegeneration.

molecular biology↗