Biology subjects

Talluri, S.

Publications and source records attributed to Talluri, S..

6 recordsLinked to original sources

bioRxiv2025

Two-colour Imaging Fluorescence Correlation Spectroscopy (ImFCS) probes the influence of the juxta-membrane actin-cortex

Here we extend Imaging Fluorescence Correlation Spectroscopy (ImFCS), together with bright, photostable fluorophores, to quantify how the juxta-membranous actin cortex influences plasma membrane dynamics. This problem is technically challenging because the membrane is only a few nanometres thick, whereas the axial resolution of live-cell fluorescence imaging is on the order of 100 nm. We address this by engineering a membrane-anchored actin reporter that combines a weakly interacting actin-binding domain with bright, photostable fluorophores optimized for two-colour ImFCS. This design enables the generation of simultaneous, co-registered diffusion maps where the mobility of the reporter serves as a dynamic sensor for the local density of the cortical actin network. The actin-binding reporter displays diffusion coefficients spanning more than two orders of magnitude, in stark contrast to an otherwise similar reporter that cannot bind actin, which diffuses much faster and within a much narrower range. Thus, the mobility of the reporter becomes a sensitive spatial readout of actin-mediated constraints. By comparing, on a pixel-by-pixel basis, the diffusion of the actin-binding reporter with that of the non-binding mutant, we construct an actin-occupancy map that quantifies the fraction of the membrane functionally influenced by cortical actin. Using this approach, we find that the juxta-membrane actin cortex modulates transport over more than 80% of the cell surface. Our two-channel ImFCS strategy establishes diffusion-based comparison as a general methodology to map the functional footprint of the cortical cytoskeleton on live cell membranes.

biophysics↗

bioRxiv2025

Active flows drive clustering and sorting of membrane components with differential affinity to dynamic actin cytoskeleton

Several cell membrane proteins, including signalling receptors and cell adhesion receptors, bind to contractile cortical F-actin at the cytoplasmic leaflet. Interaction with contractile actomyosin and associated actin flows drives these proteins into nanoscale clusters and mesoscopic assemblies of physiological relevance. In the context of diverse actin-binding membrane proteins, we ask how a specific composition of the local cluster/assembly may be achieved. Using in vitro reconstitution together with kinetic Monte Carlo simulations our studies reveal that an interplay between differential actin-binding affinity, protein-protein interactions and actomyosin remodelling leads to specific molecular patterning within a cluster and sorting between clusters. We show that in the lamellipodia of spreading cells in vivo, actin flows also result in the sorting of high and low-affinity actin-binders. This affinity-based sorting mechanism provides an attractive means for locally controlling cell membrane composition via engagement with the active cortical meshwork beneath.

cell biology↗

bioRxiv2022

ABL1 Kinase plays an important role in spontaneous and chemotherapy-induced genomic instability in multiple myeloma

Genomic instability contributes to cancer progression and is at least partly due to dysregulated homologous recombination. Here, we show that an elevated level of ABL1 kinase overactivates the HR pathway and causes genomic instability in multiple myeloma (MM) cells. Inhibiting ABL1 with either shRNA or a pharmacological inhibitor (nilotinib) inhibits HR activity, reduces genomic instability, and slows MM cell growth. Moreover, inhibiting ABL1 rescues the HR dysregulation and genomic instability caused by melphalan, a chemotherapeutic agent used in MM treatment, and increases melphalans efficacy and cytotoxicity in vivo in a subcutaneous tumor model. In these tumors, nilotinib inhibits endogenous as well as melphalan-induced HR activity. These data demonstrate that inhibiting ABL1 using the clinically approved drug nilotinib reduces MM cell growth, promotes genome stability, increases the cytotoxicity of melphalan (and similar chemotherapeutic agents), and can potentially prevent or delay progression in MM patients.

cancer biology↗

bioRxiv2022

Apurinic/apyrimidinic nuclease 1 drives genomic evolution contributing to chemoresistance and tumorigenesis in solid tumor

Genomic instability fuels genomic alterations that befit cancer cells with necessary adaptations to keep proliferating and overcome the impact of host anti-tumor immunity and cytotoxic therapy. Since DNA breaks are required for genomic rearrangements to take place, we hypothesized that dysregulated nuclease activity mediates genomic instability in cancer. Using an integrated genomics protocol, we identified a four gene deoxyribonuclease signature correlating with genomic instability in six human cancers which included adenocarcinomas of esophagus (EAC), lung, prostate, stomach, pancreas and triple negative breast cancer. Functional screens confirmed the role of these nucleases in genomic instability and growth of cancer cells. Apurinic/apyrimidinic nuclease 1 (APE1), identified as top nuclease in functional screen, was further investigated in five cell lines representing four solid tumors (EAC, lung, prostate and breast cancer). We demonstrate that chemical as well as transgenic suppression of APE1 impaired growth/colony formation and increased cytotoxicity of chemotherapeutic agent, whereas inhibited spontaneous as well as chemotherapy-induced DNA breaks, homologous recombination (HR) activity and genomic instability in all cancer cell types tested. Treatment with APE1 inhibitor also impaired tumor growth and significantly increased efficacy of a chemotherapeutic agent in a subcutaneous mouse model of EAC. Overexpression of APE1 in normal esophageal epithelial cells increased DNA breaks and HR activity, leading to massive mutational, copy number as well as karyotypic instability. Evaluation of by whole genome sequencing identified HR as the top mutational process activated by APE1. Normal cells overexpressing APE1 grew as tumors in mice and tumors removed from mice displayed additional karyotypic changes, providing evidence of genomic instability in vivo. Overall, our data demonstrate that elevated APE1 dysregulates HR activity, G2/M checkpoint and genome stability thus contributing to tumorigenesis and chemoresistance in cancer. Therefore, inhibitors of APE1 have potential to inhibit growth and increase cytotoxicity of chemotherapeutic agents while minimizing spontaneous as well as chemotherapy-induced genomic damage and instability in EAC and other solid tumors.

cancer biology↗

bioRxiv2021

Long Noncoding RNA RROL Provides Chromatin Scaffold for MYC-WDR82 Interaction to Impact Lipid Metabolism and Tumor Cell Growth in Multiple Myeloma

Long noncoding RNAs (lncRNA) can drive the tumorigenesis and be susceptible to therapeutic intervention. To define the landscape of therapeutically actionable lncRNA dependencies in multiple myeloma (MM), we coupled our extensive lncRNA transcriptomic profile with lncRNA targeted CRISPR interference viability screen and identified RNA Regulator of Lipogenesis (RROL) as a leading lncRNA dependency in MM. RROL shares its origin with the microRNA locus MIR17HG, however supports the proliferation and survival of MM cells in a microRNA- and DROSHA- independent manner. We found that RROL provides a chromatin scaffold for the functional interaction between c-MYC and WDR82 to promote the regulation of the lipogenic pathways via the transcriptional control of the rate-limiting enzyme ACC1 in MM cells. Inhibition of RROL with clinically applicable antisense molecules disrupts its transcriptional and functional activities causing potent anti-tumor effects both in vitro and in vivo in two pre-clinical animal models. This study establishes lncRNA RROL as a therapeutically actionable dependency with a unique mechanism of action in support of myeloma cell growth.

cancer biology↗

bioRxiv2020

Integrated genomics and comprehensive validation reveal novel drivers of genomic evolution in esophageal adenocarcinoma

Identification of genes driving genomic evolution can provide novel targets for cancer treatment and prevention. Here we show identification of a genomic instability gene signature, using an integrated genomics approach. Elevated expression of this signature correlated with poor survival in esophageal adenocarcinoma (EAC) as well as three other human cancers. Knockout and overexpression screens confirmed the relevance of this signature to genomic instability. Indepth evaluation of TTK (a kinase), TPX2 (spindle assembly factor) and RAD54B (recombination protein) further confirmed their role in genomic instability and tumor growth. Mutational signatures identified by whole genome sequencing and functional studies demonstrated that DNA damage and homologous recombination were common mechanisms of genomic instability induced by these genes. Consistently, a TTK inhibitor impaired EAC cell growth in vivo, and increased chemotherapy-induced cytotoxicity while inhibiting genomic instability in surviving cells. Thus inhibitors of TTK and other genes identified in this study have potential to inhibit/delay genomic evolution and tumor growth. Such inhibitors also have potential to increase chemotherapy-induced cytotoxicity while reducing its harmful genomic impact in EAC and possibly other cancers.

cancer biology↗