Biology subjects

Mahesula, S.

Publications and source records attributed to Mahesula, S..

6 recordsLinked to original sources

bioRxiv2026

Ascorbate is a physiological tumor suppressor metabolite in leukemia

Accumulation of oncometabolites promotes tumorigenesis, but it is not known if there are naturally occurring tumor suppressor metabolites whose deficiency within cancer-initiating cells causes cancer. Many leukemia patients are ascorbate deficient. Here we show that hematopoietic-specific ascorbate depletion in mice is sufficient to cause or promote leukemogenesis. Hematopoietic-specific ascorbate depletion promoted leukemogenesis by acting within leukemia initiating cells. Ascorbate depletion in myeloid leukemia expanded plasmacytoid dendritic cells, an effect mediated by the ascorbate molecular targets TET2 and TET3. Leukemia cells accumulated ascorbate as part of a tumor suppressor response to neoplastic proliferation that limited progression but depleted circulating ascorbate. Ascorbate restoration in mice with established leukemias extended survival. Hematopoietic-specific ascorbate depletion caused leukemia in collaboration with TET2 loss and was sufficient to cause leukemia with high penetrance even in the absence of other engineered mutations. These results identify ascorbate as a physiological tumor suppressor metabolite in blood cancers.

cancer biology↗

bioRxiv2025

Proteome-wide impact of LRRK1 and 2 inhibitors on protein interactions and phosphorylation

The Leucine-rich repeat kinases 1 and 2 (LRRK1 and 2) are large, multidomain proteins and closely related members of the Roco protein family. They share a high similarity in domain structure and are both phosphorylate members of the Rab GTPase family. However, despite these similarities, there are substantial differences between the two kinases. While mutations to LRRK1 are only implicated in rare cases of osteopetrosis, LRRK2 is associated with multiple diseases, most prominently with familial and sporadic forms of Parkinsons disease, where pathogenic LRRK2 is associated with an increased kinase activity. While LRRK2 has received major attention from the research community, LRRK1 has been largely understudied. In this work, we employ proximity labelling mass spectrometry in combination with quantitative phosphoproteomics in a model cell line to obtain the cellular interactomes of LRRK1 and LRRK2 and corresponding phosphorylation sites. We then use this dataset to characterize the impact of small molecules targeting both LRRK1 and 2. We identify phosphorylation sites across the proteome that are impacted by these inhibitors and identify novel candidate substrates for LRRK2, including MICALL2. Taken together our data provide a powerful resource for future studies on the cellular role and function of LRRK proteins and their potential use as therapeutic targets.

molecular biology↗

bioRxiv2025

Selectivity profiles and substrate recognition of Rab phosphorylating kinases

The Rab GTPase switch-2 region is a hotspot for post-translational modifications. Its phosphorylation can determine whether individuals develop Parkinsons disease or not. Other modifications of the same region are catalysed by enzymes from bacterial pathogens when they infect human cells. Here, we profiled a set of kinases including LRRK1, LRRK2, DYRK1A, MST1, and TBK1 for their capability of phosphorylating Rab GTPases. We identified several novel kinase:Rab pairs, such as LRRK1:Rab43 and TBK1:Rab29. Further, we comprehensively assessed what makes a Rab GTPase a good kinase substrate, considering the Rab nucleotide binding state and the Rab primary sequence. In a systematic mutational study, Rab variants with modulated phosphorylation properties were established, leading to the identification of a LRRK2 recognition patch in the Rab 3 helix. A Glu to Arg exchange in that patch increased the phosphorylation 18-fold indicating that Rabs are suboptimal LRRK2 substrates. Given that this effect is also observed in a cellular model, we propose that our variants will be excellent tools for analysing the physiological function of Rab phosphorylation.

biochemistry↗

bioRxiv2022

Loss of LRP1 in adult neural stem cells impairs migration to ischemic lesions

After ischemia, cells in the brain parenchyma upregulate stromal derived factor 1 (SDF1), driving chemokine receptor CXCR4-mediated migration of adult neural stem cells from the subventricular zone (SVZ) to the ischemic injury. We discovered a novel regulator of CXCR4 in neural stem cells, low-density lipoprotein receptor related protein 1 (LRP1). We employed a tamoxifen-inducible Nestin-Cre to drive expression of a tdTomato reporter and also knockout floxed LRP1 in adult mice and then subjected mice to middle-cerebral artery occlusion. Examination 2 weeks post-stroke reveals a loss of tdTomato positive cells localizing from the SVZ to the lesion. We show that loss of LRP1 disrupts CXCR4-mediated neural stem cell migration in vitro, which is likely driven by LRP1-mediated loss of CXCR4 expression in vivo. Altogether, our results suggest that LRP1 is a novel regulator of CXCR4 in neural stem cells. Highlights- LRP1 KO in adult neural stem cells disrupts migration to ischemic lesions in vivo. - LRP1 KO in adult neural stem cells disrupts migration towards SDF1 in vitro. - LRP1 positively regulates expression of CXCR4 in adult neural stem cells. eTOC blurbAdult neural stem cells can home to ischemic brain injury and are considered an important part of the repair process after stroke. However, little is known about what molecules help drive this response. The authors discovered that LRP1 is a novel regulator of CXCR4, which is essential for neural stem cell migration to ischemic injury.

neuroscience↗

bioRxiv2022

Antiviral function and viral antagonism of the rapidly evolving dynein activating adapter NINL

Viruses interact with the intracellular transport machinery to promote viral replication. Such host-virus interactions can drive host gene adaptation, leaving signatures of pathogen-driven evolution in host genomes. Here we leverage these genetic signatures to identify the dynein activating adaptor, ninein-like (NINL), as a critical component in the antiviral innate immune response and as a target of viral antagonism. Unique among genes encoding components of active dynein complexes, NINL has evolved under recurrent positive (diversifying) selection, particularly in its carboxy-terminal cargo binding region. Consistent with a role for NINL in host immunity, we demonstrate that NINL knockout cells exhibit an impaired response to interferon, resulting in increased permissiveness to viral replication. Moreover, we show that proteases encoded by diverse picornaviruses and coronaviruses cleave and disrupt NINL function in a host- and virus-specific manner. Our work reveals the importance of NINL in the antiviral response and the utility of using signatures of host-virus conflicts to uncover new components of antiviral immunity and targets of viral antagonism.

microbiology↗

bioRxiv2021

Cell-type specific requirement for pyruvate dehydrogenase in hematopoiesis and leukemia development.

Cancer cells have different metabolic requirements as compared to their corresponding normal tissues. This is thought to reflect metabolic reprogramming during transformation. An alternative possibility is that some metabolic requirements of cancer cells reflect a maintenance of the metabolism of the specific normal cell type from which cancer cells originate. Here, we investigate this hypothesis by comparing glucose use in normal hematopoiesis and in leukemia. T cell progenitors in the thymus were glucose avid and oxidized more glucose in the tricarboxylic acid (TCA) cycle through pyruvate dehydrogenase (PDH) as compared to hematopoietic stem cells (HSCs) or other hematopoietic cells. PDH deletion reduced the number of double positive (DP) T cell progenitors but had no effect on HSCs, myeloid progenitors and other hematopoietic cells we examined. PDH deletion blocked the development of T cell leukemia from Pten-deficient DP progenitors, but not the development of a myeloid neoplasm from Pten-deficient HSCs or myeloid progenitors. Therefore, the requirement of glucose oxidation for leukemia development is inherited from the normal cell of origin and occurs independently of the driver genetic lesion. PDH was not required in vivo to generate acetyl-CoA or maintain levels of TCA cycle metabolites but to prevent pyruvate accumulation and to maintain glutathione levels and redox homeostasis.

cancer biology↗