Biology subjects

Minotti, S.

Publications and source records attributed to Minotti, S..

5 recordsLinked to original sources

bioRxiv2024

CK1α, FAM83H, and FAM83B contribute to bundling of neurofilaments and are sequestered in cellular and mice models of ARSACS

Autosomal recessive spastic ataxia of the Charlevoix-Saguenay (ARSACS) is a rare neurodegenerative disorder characterized by mutations in the SACS gene that encodes for the sacsin protein. Sacsin dysfunction in ARSACS results in neurofilament bundling, a phenotype observed in various cellular models of ARSACS. The mechanisms underlying bundling in ARSACS remain unclear. With neurofilament phosphorylation controlling several processes of intermediate filament dynamics, its dysregulation may play a role in ARSACS. Accordingly, we investigated the interaction between CK1 (Casein Kinase 1) and its adaptor proteins FAM83H or FAM83B (FAMily with sequence similarity 83). Here, we report that these target proteins are upregulated in ARSACS patient fibroblasts and co-localize at the sites of intermediate filament bundling. In the Sacs-/- cerebellum, FAM83B compensated for the lack of FAM83H expression, suggesting a cell-type specific activity of CK1 that depends on the relative expression of its adaptor proteins. Further, CK1 inhibition with D4475 or knockdown of the target proteins with the CRISPR system caused neurofilament bundling, a phenotype that was only partially remedied by CK1 activation with SSTC3. Our findings suggest that CK1, FAM83H, and FAM83B contribute to neurofilament bundling in ARSACS; however, the inability of CK1 to resolve neurofilament bundling may reflect an error in a priming phosphorylation event in ARSACS. Future research is needed to understand the hierarchical phosphorylation cascade to CK1 activity and its contribution to ARSACS pathology. HighlightsO_LICK1 and its cell-specific adaptors are upregulated in ARSACS and targeted to the sites of bundles C_LIO_LIKnockdown of CK1, FAM83H, and FAM83B cause neurofilament bundling C_LIO_LIActivation of CK1 partially remediates bundling C_LI

cell biology↗

bioRxiv2024

Interactors of sacsin DNAJ domain identify function in organellar transport and membrane composition relevant to ARSACS pathogenesis

Autosomal Recessive Spastic Ataxia of the Charlevoix Saguenay (ARSACS) is caused by loss of function mutations in the SACS gene encoding sacsin, a 520kDa protein with multiple functional domains. The goal of this study was to identify client proteins interacting with the J domain, a cochaperone domain interacting with Hsp70 chaperones, to gain insights into sacsins function and its disruption in experimental models of ARSACS. Pull downs from mouse brain identified Rabs and Rab-associated proteins including Rab1b, ARF5 and endophilin B2, involved in organelle trafficking. In cell and mouse models of ARSACS, higher molecular weight species of Rab1b were identified on SDS-PAGE in addition to the normal 25kDa band and Rab1was retained in the soma along with membranous organelles (i.e., ER, Golgi and ATG9 autophagic vesicles). These changes were reversed by expression of the DNAJ domain or the Ubl domain of sacsin and occurred independent of the formation of abnormal bundles of intermediate filaments, a key feature of ARSACS. Although Rab1b was associated with both Golgi and ER in both Sacs+/+ and Sacs-/- cells, expression of the DNAJ domain or the Ubl domain of sacsin increased Rab1b association with ER and restored normal electrophoretic mobility. Finally, subcellular distribution of another membrane protein, neuroplastin, a key receptor for synapse formation and plasticity, also was impaired, pointing to a general problem in Rab-dependent membrane trafficking in the absence of sacsin.

cell 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↗

bioRxiv2021

The J domain of sacsin disrupts intermediate filament assembly

Autosomal Recessive Spastic Ataxia of the Charlevoix Saguenay (ARSACS), is caused by loss of function mutations in the SACS gene, which encodes sacsin, a giant protein of 520 kDa. A key feature of the absence of sacsin in cells is the formation of abnormal bundles of intermediate filaments (IF) including neurofilaments (NF) in neurons and vimentin IF in fibroblasts, suggesting a role of sacsin in IF homeostasis. Sacsin contains a J domain (SacsJ) homologous to Hsp40, that can interact with Hsp70 chaperones. The SacsJ domain resolved NF bundles in cultured Sacs-/- neurons, however, its mechanism is still unclear. Here, we focused on the role of SacsJ in NF assembly. We report that the SacsJ domain directly interacts with NF proteins in vitro to disassemble NFL filaments, and to inhibit their initial assembly, in the absence of Hsp70. We generated a cell-penetrating peptide derived from this domain, SacsJ-myc-TAT, which was efficient in disassembling both vimentin IF and NF in cultured fibroblasts and Sacs+/+ motor neurons as well as NF bundles in cultured Sacs-/- motor neurons. Whereas a normal NF network was restored in Sacs-/- neurons treated with the SacsJ peptide, there was some loss of IF networks in Sacs+/+ fibroblasts or neurons. These results suggest that SacsJ is a key regulator of NF and IF networks in cells, with implications for its therapeutic use.

cell biology↗