Biology subjects

Itkin-Ansari, P.

Publications and source records attributed to Itkin-Ansari, P..

5 recordsLinked to original sources

bioRxiv2025

A knowledge-guided approach to recovering important rare signals from high-dimensional single-cell data

Single-cell transcriptomic data are high-dimensional, with many genes profiled in each cell. Dimensionality reduction is routinely applied to improve interpretability, remove noise and redundancy, and enable visualization. Most existing methods aim at preserving the most prominent data properties, which can lead to omission of rare but important signals. Here we propose a novel framework that uses knowledge-derived genes of interest to guide dimensionality reduction, which can help cluster rare cells and separate highly similar cell sub-populations. We demonstrate the utility of our framework in identifying endocrine cell subtypes in the pancreatic islet, highly similar hematopoietic sub-populations, and rare senescent cells.

bioinformatics↗

bioRxiv2023

Bone Morphogenetic Protein (BMP) signaling upregulates expression of the E protein repressors, ID1 and ID3, in pancreatitis and pancreatic ductal adenocarcinoma

Identification of biological modulators of pancreatic ductal adenocarcinoma (PDAC) initiation and progression is of critical importance as it remains one of the deadliest cancers. We have previously shown that ID1 and ID3 are highly expressed in human PDAC and function to repress expression of E47 target genes involved in acinar cell differentiation and quiescence. Here, mining of large bulk RNA-seq and single cell RNA-seq (scRNA-seq) datasets has associated high expression of ID1 and ID3 with poor PDAC patient survival. We show that upregulated expression of ID1 and ID3 in human PDAC cells occurs in response to canonical BMP signaling through pSMAD1/5/9. Conversely, treatment with Noggin, an endogenous BMP antagonist, or with DMH1 and LDN193189, small molecule inhibitors of BMP receptors, reduced expression of ID1, ID3 and cell cycle control genes. Based on our RNA-seq and immunohistochemical analyses, upregulation of BMP signaling to ID1 and ID3 is an early event that occurs in human pancreatic intraepithelial neoplasia (PanIN) and murine models of pre-neoplastic lesions induced by mutant Kras. Strikingly, the same result was observed in a murine model of pancreatitis induced by the cholecystokinin (CCK) analog caerulein. Moreover, we show that caerulein is sufficient to induce BMP signaling and expression of ID1 and ID3 in a cell-autonomous manner in non-transformed rodent exocrine pancreas cells. Together, the data suggest that canonical BMP signaling upregulates expression of ID1 and ID3 early in pancreas pathogenesis and that pancreatic cancer cells remain addicted to this important signaling circuit as the disease progresses. Future exploration of druggable targets within this pathway could be of therapeutic benefit in the treatment of pancreatitis and PDAC.

cancer biology↗

bioRxiv2022

Inflammatory cytokines rewire the proinsulin interaction network in human islets

Aberrant biosynthesis and secretion of the insulin precursor proinsulin occurs in both Type I and Type II diabetes (T1D, T2D). Inflammatory cytokines are implicated in pancreatic islet stress in both forms of diabetes but the mechanisms remain unclear. Here we examined how the diabetes associated cytokines interleukin-1{beta} and interferon-{gamma} alter proinsulin interactions with proteins that regulate its folding, trafficking, and secretion. Human islets treated with cytokines exhibited secretion of proinsulin, IL6 and nitrite, as well as evidence of endoplasmic reticulum (ER) stress. Unbiased proinsulin Affinity Purification-Mass Spectrometry revealed a proinsulin interactome reshaped by cytokines relative to controls. Cytokine treatment increased proinsulin binding to multiple ER chaperones and oxidoreductases, including the major ER chaperone BiP. Moreover, increased BiP binding was an adaptive response required to maintain proinsulin folding in the inflammatory environment. Cytokines also regulated novel interactions between proinsulin and T1D and T2D GWAS candidate proteins not previously known to interact with proinsulin (e.g., Ataxin-2) and these GWAS proteins formed a tight network with each other. Finally, cytokines induced proinsulin interactions with a cluster of microtubule motor proteins. Consistent with a role for these proteins in proinsulin trafficking and release, chemical destabilization of microtubules with Nocodazole exacerbated cytokine induced proinsulin secretion. Together, the data quantitatively map the proinsulin interactome rewired by cytokines, shedding new light on how human proinsulin biosynthesis is dysregulated by an inflammatory environment.

cell biology↗

bioRxiv2019

Role of Proinsulin Self-Association in Mutant INS gene-induced Diabetes of Youth

Abnormal interactions between misfolded mutant and wild-type (WT) proinsulin in the endoplasmic reticulum (ER) drive the molecular pathogenesis of Mutant-INS-gene induced Diabetes of Youth (MIDY). How these abnormal interactions are initiated remains unknown. Normally, proinsulin-WT dimerizes in the ER. Here, we suggest that the normal proinsulin-proinsulin contact surface, involving the B-chain, contributes to dominant-negative effects of misfolded MIDY mutants. Specifically, we find that proinsulin Tyr-B16, which is a key residue in normal proinsulin dimerization, helps confer dominant-negative behavior of MIDY mutant proinsulin-C(A7)Y. Substitutions of Tyr-B16 with ether Ala, Asp, or Pro in proinsulin-C(A7)Y each decrease the abnormal interactions between the MIDY mutant and proinsulin-WT, rescuing proinsulin-WT export, limiting ER stress, and increasing insulin production in {beta}-cells and human islets. This study reveals the first evidence indicating that noncovalent proinsulin-proinsulin contact initiates dominant-negative behavior of misfolded proinsulin, pointing to a novel therapeutic target to enhance bystander proinsulin export for increased insulin production.

cell biology↗

bioRxiv2019

A reference map of the human proinsulin biosynthetic interaction network

The beta-cell protein synthetic machinery is dedicated to the production of insulin, which plays a critical role in organismal homeostasis. Insulin synthesis requires the proper folding and trafficking of its precursor, proinsulin, yet the precise network of proinsulin protein interactions in the secretory pathway remains poorly defined. In the present study we conducted unbiased profiling of the proinsulin interactome in human islets, utilizing a human proinsulin-specific monoclonal antibody for affinity purification and mass spectrometry. Stringent analysis identified a central node of interactions between human proinsulin and sequential secretory pathway proteins that is remarkably conserved across 3 ethnicities and both genders. Among the most prominent proinsulin interactions was with ER-localized peroxiredoxin-4 (PRDX4). A functional role for PRDX4 in beta-cells was demonstrated by gene silencing that rendered proinsulin susceptible to misfolding, particularly in response to oxidative stress. Conversely, exogenous PRDX4 improved proinsulin folding. Notably, oxidative stress and even high glucose treatment alone induced proinsulin misfolding in human islets and MIN6 cells, and this was accompanied by sulfonylation of PRDX4, a modification known to inactivate peroxiredoxins. This finding prompted PRDX4 analysis in a panel of human islet samples that revealed significantly higher levels of sulfonylated (inactive) PRDX4 in islets from patients with T2D compared to that of healthy individuals. Taken together, these data highlight the importance of elucidating the complete proinsulin interactome in human islets in order to understand critical steps controlling insulin biosynthesis, beta cell function, and T2D.

biochemistry↗