Biology subjects

Qureshi, S.

Publications and source records attributed to Qureshi, S..

5 recordsLinked to original sources

bioRxiv2026

Sonic Hedgehog Is An Important Regulator Of Intervertebral Disc Homeostasis And Rejuvenation

Intervertebral disc degeneration and associated neurological symptoms constitute a global health burden, yet no cure is currently available (1,2). Each disc consists of a central nucleus pulposus, surrounded by annulus fibrosus, and end plates connecting it to the growth plates of adjacent vertebral bodies. The notochord-descendant nucleus pulposus continues to express sonic hedgehog, which regulates the proliferation and differentiation of all components of neonatal mouse discs (3-7). Sonic hedgehog expression and function decline with age and are associated with disc pathologies, including terminal differentiation of nucleus pulposus cells to chondrocyte-like phenotype (7,8). Here, we used fate-mapping and conditional genetic mouse models to test the role of sonic hedgehog in the homeostasis of aging discs. We found that loss of NP-derived Shh is sufficient to accelerate multiple features of age-associated disc degeneration, including reduced NP cell number, altered matrix turnover, and induction of inflammatory, angiogenic and neurotrophic programs. Age-related disc pathologies were more prevalent in the lumbosacral discs of mice, like in humans (8-13). Also, like mice, the expression of sonic hedgehog and its targets by human nucleus pulposus cells declines with age and pathological degeneration. Moreover, pharmacologic Hedgehog activation partially restored anabolic gene expression and reduced catabolic, inflammatory and neurotrophic mediators in degenerated human NP explants ex vivo. These findings indicate that Sonic hedgehog, a developmental signal retained in the adult NP, is functionally active and required for disc homeostasis during aging and supports activation of hedgehog signaling as a candidate disease-modifying pathway for intervertebral disc pathologies.

developmental biology↗

bioRxiv2026

Preclinical trial supports dual inhibition of BCL2 and Aurora kinase A for MYCN-amplified high-risk neuroblastoma

Purpose: Treatment for children with high-risk neuroblastoma relies on conventional chemotherapy and anti-GD2 immunotherapy. However, 5-year survival is only 50%, with high rates of late effects. Targeted therapy combinations are a major priority for these patients. The BCL2 inhibitor venetoclax, in combination with cyclophosphamide/topotecan, has clinical activity in relapsed and refractory neuroblastoma. We sought more effective and safer venetoclax combinations through systematic preclinical testing. Experimental design: Synergistic combinations were identified by high-throughput screening using patient-derived xenograft (PDX) models and confirmed in vivo. The leading combination (venetoclax-alisertib) was compared to combination chemotherapy in a clinical trial-like study using 22 PDX models, in scheduling experiments designed to reduce short-term toxicity, and in combination with anti-GD2 immunotherapy. BCL2 and Bim-BCL2 complex protein levels were assessed as predictors of sensitivity. Results: In vitro synergy with venetoclax was observed for standard-of-care chemotherapies and targeted agents, including DNA topoisomerase, microtubule, HDAC and Aurora kinase A (AURKA) inhibitors. Venetoclax-alisertib was particularly effective in vivo. In an n=1 study, venetoclax-alisertib induced objective response in all models. Activity was most striking in models of MYCN-amplified disease (n=12), doubling median survival time compared to cyclophosphamide/topotecan, and outperforming venetoclax-cyclophosphamide-topotecan. Efficacy was maintained with discontinuous schedules, minimizing hematological toxicity without substantially compromising activity. PDX-engrafted animals treated with venetoclax-alisertib and anti-GD2 immunotherapy survived tumor-free long-term. BCL2 expression and BCL2-Bim complex levels were of limited value for predicting response. Conclusion: Our findings support advancement of BCL2-AURKA inhibition to clinical trial for neuroblastoma with or without anti-GD2 immunotherapy, particularly in patients with MYCN amplified disease.

cancer biology↗

bioRxiv2026

Chronic ER Stress Disrupts Mitochondrial-Associated ER Membrane Integrity in Corneal Endothelial Cells.

PurposeFuchs endothelial corneal dystrophy (FECD) is an age-related degenerative disease of the corneal endothelium cells (CEnCs), affecting 4% of the US population over 40. While Endoplasmic reticulum (ER) and mitochondrial stress have been independently associated with FECD pathogenesis, few studies have examined ER-mitochondrial interactions/ER-mitochondrial contact sites/mitochondria-associated ER membrane (MAM), or MAM proteins, and their contribution to ER and mitochondrial stress in FECD. This study aims to characterize alterations in MAMs and identify key MAM proteins associated with ER and mitochondrial stress in FECD. MethodHuman corneal endothelial cell line (HCEnC-21T) and Fuchs corneal endothelial cell line (F35T) were cultured and subjected to ER stressor tunicamycin (1, 10 g/ml) for 6 and 24 hours. MAM proteins were isolated by subcellular fractionation, and key ER and mitochondrial-damage-sensor proteins, such as PERK and Parkin, respectively, were identified by immunoblotting. ER-mitochondrial contact sites were quantified using the MAM plasmid and transmission electron microscopy (TEM) in normal and Fuchs cell lines, as well as in human tissues under chronic ER stress. ResultsER-mitochondrial contact distance significantly increased in Fuchs tissues compared with normal tissues, and a similar increase was observed in 21T cell line after tunicamycin treatment. There was a significant increase in the intensity of the MAM plasmid upon tunicamycin treatment at 6 hours in the 21T cell line compared to the non-treated control. However, MAM plasmid intensity significantly decreased at 24 hours compared to 6 hours post-tunicamycin treatment in 21T cell line. Analysis of MAM function by quantifying phosphatidylserine synthase 1 (PSS1 [gene PTDSS1]) expression in 21T cells showed a reduction in PTDSS1 expression after 24 hours of tunicamycin treatment. ER stress protein PERK and mitochondria damage sensor protein (Parkin) significantly increased in the MAM fraction after tunicamycin at 24 hours in 21T cell line. ConclusionsFuchs cell lines and tissues demonstrate decreased ER-mitochondrial interactions/MAMs, which are also seen in 21T cell line after chronic ER stress. Under chronic ER stress, ER and mitochondrial stress mediator proteins are translocated to MAM. This study highlights the importance of MAMs as a potential mediator of ER-mitochondria crosstalk in degenerating corneal endothelial cells for FECD.

cell biology↗

bioRxiv2024

ATF4 regulates mitochondrial dysfunction, mitophagy, and autophagy, contributing to corneal endothelial apoptosis under chronic ER stress in Fuchs dystrophy

PURPOSEEndoplasmic reticulum (ER) stress, mitochondrial dysfunction, and mitophagy are known to contribute independently to corneal endothelial cell (CEnC) apoptosis in Fuchs endothelial corneal dystrophy (FECD). However, the role of a specific ER stress pathway (PERK-ATF4-CHOP) in regulating these events is unknown. This study aims to investigate the role of ATF4 in regulating mitochondrial dysfunction and mitophagy, which ultimately leads to CEnC apoptosis in FECD. METHODSHuman corneal endothelial cell line (21T), Fuchs corneal endothelial cell line (F35T), and primary human corneal endothelial cells were treated with ER stressor tunicamycin (Tun). ATF4 siRNA was used to knock down ATF4 in 21T cell line and primary corneal endothelial cells. Mitophagy and apoptotic proteins were analyzed using Western blotting. ATF4+/- and ATF4 +/+ mice were irradiated with UVA to assess ER stress and corneal endothelial apoptosis. RESULTSF35T cell line had significantly increased expression of the ER stress pathway as well as caspase-mediated apoptotic molecules compared to 21T at baseline, which further increased after tunicamycin treatment. F35T cells exhibited significantly decreased ATP and MMP, and increased mitochondrial fragmentation, which was further exacerbated after Tunicamycin. F35T cell line also demonstrated inhibition of mitophagy, similar to 21T, after treatment with Tunicamycin, despite the upregulation of mitophagy initiators. ATF4 knockdown attenuated ER and mitochondrial stress proteins, rescued mitochondrial membrane potential (MMP) loss, downregulated mitochondrial fragmentation, activated mitophagy, and prevented cell death under chronic ER stress. ATF4+/-mice had increased CE numbers, with improved cellular morphology and decreased ER stress CHOP expression, compared to ATF4+/+ mice post-UVA. CONCLUSIONSPro-apoptotic ATF4 induction following ER stress disrupts mitochondrial function, leading to mitophagy inhibition and CEnC apoptosis. This study highlights the importance of ATF4 in ER-mitochondrial crosstalk and its contribution to CEnC apoptosis in FECD.

cell biology↗

bioRxiv2022

CXCL12 in late-stage osteoblasts and osteocytes is required for load induced bone formation in mice

Increased physical loading of the skeleton activates new bone formation ensuring its ability to meet mechanical demands over time; however, the capacity of bone to respond to mechanical stimulation diminishes with age. Osteocytes, the cells embedded and dispersed throughout mineralized bone matrix, are master regulators of mechanoadaptation through recruitment of new bone-forming cells, the osteoblasts, via signaling to osteoprogenitors located on bone surfaces. We previously demonstrated that in vivo and in vitro mechanical stimulation significantly upregulated the chemokine C-X-C Motif Chemokine Ligand 12 (CXCL12) and its receptor, CXCR4, in osteocytes and bone lining cells, and that CXCR4 antagonism with AMD3100 attenuated in vivo load-induced bone formation. Here, we extended this work by showing that ablation of CXCL12+ cells and deletion of cxcl12 in late-stage osteoblasts and osteocytes significantly attenuated in vivo load-induced bone formation in the mouse tibia. This bone loading phenotype was rescued by treatment with recombinant CXCL12. To address mechanism, we showed that in vitro deletion of cxcl12 and cxcr4, separately, in bone marrow stromal cells resulted in significantly reduced osteogenic differentiation. Furthermore, CXCL12 treatment enhanced GSK-3b phosphorylation and {beta}-catenin translocation to the nucleus, the former of which was partially blocked by AMD3100. Finally, CXCL12 synergized Wnt signaling leading to significantly increased total {beta}-catenin protein and Axin2 expression, a Wnt signaling target gene. These findings together demonstrate that CXCL12 expression in late-stage osteoblasts and osteocytes is essential for load-induced bone formation, in part, by regulating osteogenic differentiation through activation of the Wnt signaling pathway. SignificanceSkeletal adaptation to mechanical loading is contingent on the recruitment of new osteoblasts to bone surfaces. CXCL12, a chemokine expressed by osteolineage cells, targets effector cells expressing its receptor CXCR4, including osteoprogenitors. Exogenous mechanical loading of mouse hind limbs upregulates CXCL12 in osteocytes, bone lining cells and marrow cells, while antagonizing CXCR4 led to significantly attenuated load-induced bone formation. Here, we show that CXCL12 expression in late-stage osteoblasts and osteocytes is required for load-induced bone formation. Treatment with recombinant CXCL12 rescued the bone loading phenotype suggesting that the CXCL12/CXCR4 signaling pathway may be a feasible drug target for promoting load-induced bone formation when exercise alone is insufficient to counteract low bone mass and osteoporosis.

cell biology↗