Biology subjects

Rokka, A.

Publications and source records attributed to Rokka, A..

5 recordsLinked to original sources

bioRxiv2024

Functionality of BRCA1 supports the survival of prostate cancer cells during the development of castration resistance

Androgen deprivation therapy (ADT; castration) is the main treatment option for metastatic prostate cancer (PCa), but eventually, castration-resistant prostate cancer (CRPC) develops with no curative treatments. In CRPC, more than 20% of men carry mutations in DNA damage response (DDR) genes, including BRCA1/2. In this study, we elucidated the prostate tissue-specific functional role of BRCA1 protein. Our results indicate that DDR is dynamically regulated by androgen receptor (AR) signaling, and AR activation by the natural ligand dihydrotestosterone strongly downregulates the expression of BRCA1 in multiple cell lines. Consistent with these findings, our analyses of patient samples and mouse xenografts showed that DNA damage and BRCA1 expression were sustained after ADT. With unbiased mass spectrometry and bioinformatics approaches as well as experimentally, we found that BRCA1 interacts with Raptor, an mTORC1 component, and regulates the mTOR signaling pathway and PCa growth in vitro. Furthermore, we found that mTOR inhibition reduced the recruitment of DDR proteins, BRCA1 and Rad51, to DNA damage sites, creating a vulnerability towards DNA damage-inducing androgen deprivation. Moreover, we observed that BRCA1 supported ADT-induced activation of the oxidative stress sensor NRF2. Our findings shed further light on the complex DDR-AR interplay in PCa and suggest that, during PCa progression, BRCA1 expression may be retained due to the beneficial modulation of mTORC1 signaling in the AR environment by BRCA1. SignificanceAndrogen receptor activation acts as a strong suppressor of BRCA1. Consequently, androgen deprivation activates BRCA1, which in turn promotes survival in castration resistance by supporting mTOR signaling and NRF2-mediated antioxidant processes.

cancer biology↗

bioRxiv2019

CRK2-mediated control of ROS production by phosphorylation of the RBOHD C-terminus in Arabidopsis

Reactive oxygen species (ROS) are important messengers in eukaryotic organisms and their production is tightly controlled. Active extracellular ROS production by NADPH oxidases in plants is triggered by receptor-like protein kinase (RLK)-dependent signaling networks. Here we show that the cysteine-rich RLK CRK2 kinase activity is required for plant growth and CRK2 exists in a preformed complex with the NADPH oxidase RBOHD in Arabidopsis. Functional CRK2 is required for the full elicitor-induced ROS burst and consequently the crk2 mutant is impaired in defense against the bacterial pathogen Pseudomonas syringae pv. tomato DC3000. Our work demonstrates that CRK2 regulates plant innate immunity. We identified in vitro CRK2-dependent phosphorylation sites in the C-terminal region of RBOHD. Phosphorylation of S703 RBOHD is enhanced upon flg22 treatment and substitution of S703 with alanine reduced ROS production in Arabidopsis. Phylogenetic analysis suggests that phospho-sites in C-terminal region of RBOHD are conserved throughout the plant lineage and between animals and plants. We propose that regulation of NADPH oxidase activity by phosphorylation of the C-terminal region might be an ancient mechanism and that CRK2 is an important element in regulating MAMP-triggered ROS production. One-sentence summaryCRK2 associates with and activates RBOHD to trigger MAMP-induced ROS production and reveals a novel regulatory mechanism for plant NADPH oxidases through phosphorylation of the C-terminus.

plant biology↗

bioRxiv2018

CRK2 enhances salt tolerance in Arabidopsis thaliana by regulating endocytosis and callose deposition in connection with PLDα1

High salinity has become an increasingly prevalent source of stress to which plants need to adapt. The receptor-like protein kinases (RLKs), including the cysteine-rich receptor-like kinase (CRK) subfamily, are a highly expanded family of transmembrane proteins in plants and are largely responsible for communication between cells and the extracellular environment. Various CRKs have been implicated in biotic and abiotic stress responses, however their functions on a cellular level remain largely uncharacterized. Here we have shown that CRK2 enhances salt tolerance at the germination stage in Arabidopsis thaliana. We identified CRK2 as a negative regulator of endocytosis, under both normal growth conditions and salt stress. We also established that functional CRK2 is required for salt-induced callose deposition. In doing so, we revealed a novel role for callose deposition, in response to increased salinity, and demonstrated its importance for salt tolerance during germination. Using fluorescently tagged proteins we observed specific changes in CRK2s subcellular localization in response to various stress treatments. Many of CRK2s cellular functions were dependent on phospholipase D (PLD) activity, as were the subcellular localization changes. Thus we propose that CRK2 acts downstream of PLD during salt stress to regulate endocytosis and promote callose deposition, and that CRK2 adopts specific stress-dependent subcellular localization patterns in order to carry out its functions.\n\nOne sentence summaryThe receptor-like kinase CRK2 acts in connection with PLD1 to regulate endocytosis and callose deposition at plasmodesmata, enhancing salt tolerance in Arabidopsis thaliana.

plant biology↗

bioRxiv2018

Data-independent acquisition mass spectrometry enables reproducible characterization of microbiota function

Metaproteomics is an emerging research area which aims to reveal the functionality of microbial communities - unlike the increasingly popular metagenomics providing insights only on the functional potential. So far, the common approach in metaproteomics has been data-dependent acquisition mass spectrometry (DDA). However, DDA is known to have limited reproducibility and dynamic range with samples of complex microbial composition. To overcome these limitations, we introduce here a novel approach utilizing data-independent acquisition (DIA) mass spectrometry, which has not been applied in metaproteomics of complex samples before. For robust analysis of the data, we introduce an open-source software package diatools, which is freely available at Docker Hub and runs on various operating systems. Our highly reproducible results on laboratory-assembled microbial mixtures and human fecal samples support the utility of our approach for functional characterization of complex microbiota. Hence, the approach is expected to dramatically improve our understanding on the role of microbiota in health and disease.

microbiology↗

bioRxiv2018

GGA2 and RAB13 regulate activity-dependent β1-integrin recycling

{beta}1-integrins mediate cell-matrix interactions and their trafficking is important in the dynamic regulation of cell adhesion, migration and malignant processes like cancer cell invasion. Here we employ an RNAi screen to characterize regulators of integrin traffic and identify the association of Golgi-localized gamma ear-containing Arf-binding protein 2 (GGA2) with {beta}1-integrin and its role in recycling of the active but not inactive {beta}1-integrin receptors. Silencing of GGA2 limits active {beta}1-integrin levels in focal adhesions and decreases cancer cell migration and invasion congruent with its ability to regulate the dynamics of active integrins. Using the proximity-dependent biotin identification (BioID) method, we identify two RAB family small GTPases, RAB13 and RAB10, associating with GGA2 and {beta}1-integrin. Functionally, RAB13 silencing triggers the intracellular accumulation of active {beta}1-integrin, reduces integrin activity, in focal adhesions, and cell migration, similarly to GGA2 depletion, indicating that both facilitate active {beta}1-integrin recycling the plasma membrane. Thus, GGA2 and RAB13 are important specificity determinants for integrin activity-dependent traffic.

cell biology↗