Biology subjects

Olson, M. F.

Publications and source records attributed to Olson, M. F..

10 recordsLinked to original sources

bioRxiv2026

Sec23b regulates cell migration by orchestrating collagen I secretion and processing.

Cell migration is critically important for development and for homeostatic processes such as wound healing, while its aberrant regulation may contribute to the development of pathological conditions and diseases. Efficient cell migration requires the coordination of many structural and signalling proteins (e.g. Rho GTPases) that have key functions in controlling actin cytoskeleton organization and dynamics. Given that the actin cytoskeleton has a central role in orchestrating the complex series of events underlying cell migration, characterizing the actin-associated proteome can illuminate important molecular players that could be novel therapeutic targets for diseases associated with dysregulated cell migration. Here, we report a proteomic-based assay that uses a doxycycline-inducible proximity ligation assay to label actin-associated proteins (actin cytoskeletome) during the early stages of cell migration. We found that an unexpected actin-associated protein, Sec23b, influences the rate of cell migration by orchestrating the secretion and post-secretion maturation of Collagen I.

cell biology↗

bioRxiv2026

MRCKα represses GEF-H1 mediated RhoA activation to promote ovarian cancer spheroid growth and invasion.

High-grade serous ovarian carcinoma (HGSOC) is characterized by high mortality rates and the frequent development of chemotherapy resistance. A hallmark of HGSOC progression is the formation of multicellular spheroids in malignant ascites that facilitate peritoneal dissemination and metastasis. While the CDC42-regulated kinases MRCK and MRCK{beta} (MRCK) were previously found to be highly expressed in ovarian tumors and to be essential for cell migration and spheroid growth, the underlying molecular mechanisms were poorly defined. Mass spectrometry identified the RhoA-selective guanine nucleotide exchange factor GEF-H1 as a primary interacting partner of MRCK. Functional assays revealed that MRCK inhibition or knockdown led to significantly increased levels of active GEF-H1 and subsequent RhoA activation. MRCK was found to phosphorylate GEF-H1 on Ser174, and pharmacological inhibition of MRCK reduced this phosphorylation and decreased the association of GEF-H1 with -Tubulin. Live-cell imaging and 3D assays demonstrated that MRCK inhibition disrupted cell-cell contacts and impaired the compaction of multicellular structures, ultimately reducing the viability of patient-derived organoids. These findings delineate a novel signaling crosstalk mechanism in which MRCK represses GEF-H1-mediated RhoA activation to facilitate the formation of cell-cell contacts that contribute to the survival and growth of HGSOC cells in 3D multicellular structures. This study highlights MRCK as a potential therapeutic target to inhibit the growth and spread of HGSOC.

cell biology↗

bioRxiv2025

Radiotherapy drives lung metastasis in PDAC via a RhoGTPasesignaling shift towards MRCK-dependency

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive cancer with an extremely poor prognosis, partly owing to its highly metastatic nature. Although radiotherapy is an effective and potentially curative treatment modality, research over the last few decades has indicated that it may induce a more metastatic phenotype in surviving cancer cells. We demonstrate for the first time that clinically relevant doses of image-guided targeted radiotherapy induce metastasis in a genetically engineered KPC mouse model of PDAC. Furthermore, this induction is largely driven by an organotropic switch towards lung metastasis. Using an in vitro RNAi screening approach, we identified a key role for myotonic dystrophy-related Cdc42-binding kinase (MRCK) in driving this response. MRCK activity was spatially upregulated at the plasma membrane in response to radiotherapy in PDAC cell lines as well as at the invasive margins of PDAC tumors. This upregulation of activity was maintained in metastases, suggesting an important role for MRCK in not only triggering local invasion in response to radiotherapy but also promoting distant metastases. Importantly, inhibition of MRCK with a small-molecule inhibitor (BDP9066) specifically opposed radiation-driven MRCK upregulation and pro-metastatic response.

cancer biology↗

bioRxiv2025

Toggle-Untoggle: A cell segmentation tool with an interactive user verification interface.

Accurate cell segmentation is an essential step in the quantitative analysis of fluorescence microscopy images. Pre-trained deep learning models for automatic cell segmentation, such as Cellpose, offer strong performance across a variety of biological datasets but may still introduce segmentation errors. While training custom models can improve accuracy, it often requires programming expertise and significant time, limiting the accessibility of automatic cell segmentation for many wet lab researchers. To address this gap, we developed "Toggle-Untoggle", a desktop application that combines automated segmentation using the Cellpose "cyto3" model with a user-friendly graphical interface for intuitive segmentation quality control. Our app allows users to refine results by interactively toggling individual segmented cells on or off without the need to manually edit segmentation masks, and to export morphological data and cell outlines for downstream analysis. Here we demonstrate the utility of "Toggle-Untoggle" in enabling accurate, efficient single-cell analysis on real-world fluorescence microscopy data, with no coding skills required.

bioinformatics↗

bioRxiv2024

Caspase-resistant ROCK1 expression prolongs survival of E-mu-Myc B cell lymphoma mice.

Apoptosis is characterized by membrane blebbing and apoptotic body formation. Caspase cleavage of ROCK1 generates an active fragment that promotes actin-myosin mediated contraction and membrane blebbing during apoptosis. Expression of caspase-resistant non-cleavable ROCK1 (Rock1 NC) prolonged survival of mice that rapidly develop B cell lymphomas due to E{micro}-Myc transgene expression. E{micro}-Myc; Rock1 NC mice had significantly fewer bone marrow cells relative to E{micro}-Myc mice expressing wild-type ROCK1 (Rock1 WT), which was associated with altered cell cycle profiles. Circulating macrophage numbers were lower in E{micro}-Myc; Rock1 NC mice, but there were higher levels of bone marrow macrophages, consistent with spontaneous cell death in E{micro}-Myc; Rock1 NC mice bone marrows being more inflammatory. Rock1 WT recipient mice transplanted with pre-neoplastic E{micro}-Myc; Rock1 NC bone marrow cells survived longer than mice transplanted with E{micro}-Myc; Rock1 WT cells, indicating that the survival benefit was intrinsic to the E{micro}-Myc; Rock1 NC bone marrow cells. The results suggest that the apoptotic death of E{micro}-Myc; Rock1 NC cells generates a proliferation-suppressive microenvironment in bone marrows that reduces cell numbers and prolongs B cell lymphoma mouse survival.

cancer biology↗

bioRxiv2022

Apoptotic contraction drives target cell release by cytotoxic T cells

Cytotoxic T lymphocytes (CTLs) use immune synapses to destroy infected or transformed target cells. Although the mechanisms governing synapse assembly have been studied extensively, little is known about how this interface dissociates, which is a critical step that both frees the CTL to search for additional prey and enables the phagocytosis of target corpses. Here, we applied time-lapse imaging to explore the basis for synapse dissolution and found that it occurred concomitantly with the cytoskeletal contraction of apoptotic targets. Genetic and pharmacological disruption of apoptotic contraction indicated that it was necessary for CTL dissociation. Furthermore, acute stimulation of contractile forces triggered the release of live targets, demonstrating that contraction is sufficient to drive the response. Finally, mechanically amplifying apoptotic contractility promoted faster CTL detachment and serial killing. Collectively, these results establish a biophysical basis for synapse dissolution and highlight the importance of mechanosensory feedback in the regulation of cell-cell interactions.

immunology↗

bioRxiv2022

Actomyosin-mediated cellular tension promotes Yap nuclear translocation and myocardial proliferation through alpha5 integrin signaling

The cardiomyocyte phenotypic switch from a proliferative to terminally differentiated state results in the loss of regenerative potential of the mammalian heart shortly after birth. Yet, the molecular mechanisms that regulate this critical developmental process are incompletely understood. Nonmuscle myosin IIB (NM IIB)-mediated actomyosin contractility regulates cardiomyocyte cytokinesis in the embryonic heart, and NM IIB levels decline after birth suggesting a role for cellular tension in the regulation of cardiomyocyte cell cycle activity in the postnatal heart. The Rho kinase (ROCK) serine/threonine protein kinases that act downstream of the RhoA small GTP-binding protein regulate nonmuscle myosin contractile force generation. To investigate the role of actomyosin contractility in cardiomyocyte maturation and cell cycle arrest, we conditionally-activated ROCK2 kinase domain (ROCK2:ER) in the murine postnatal heart. Here we show that cardiac-specific activation of actomyosin contractility shifts the balance from cell-cell to cell-matrix adhesions. Specifically, 5/{beta}1 integrin and fibronectin matrix increase in response to actomyosin-mediated tension. Moreover, activation of ROCK2:ER promotes nuclear translocation of Yap, a mechanosensitive transcriptional co-activator, and enhances cardiomyocyte proliferation. Finally, we show that reduction of myocardial 5 integrin rescues the myocardial proliferation phenotype in ROCK2:ER hearts. These data demonstrate that cardiomyocytes respond to increase intracellular tension by altering their intercellular contacts in favor of cell-matrix interactions leading to Yap nuclear translocation, thus uncovering a novel function for nonmuscle myosin contractility in promoting cardiomyocyte cell cycle activity in the postnatal heart.

developmental biology↗

bioRxiv2022

Immunogenic cell death in mice expressing caspase-resistant ROCK1 is not replicated by ROCK inhibitors

The characteristic changes in morphology during apoptosis help facilitate "immunologically-silent" cell death by limiting the release of cellular contents and enabling efficient clearance of apoptotic cell bodies. Caspase-mediated cleavage of the ROCK1 protein kinase results in its constitutive activation, which drives the rapid and forceful contraction of apoptotic cells. We previously showed in Julian et al. [1] that when ROCK1 was mutated to render it caspase-resistant, there was greater liver damage and neutrophil recruitment after acute treatment with the hepatotoxin diethylnitrosamine (DEN). We now show that acute DEN-induced liver damage resulted in greater induction of pro-inflammatory cytokines/chemokines, indicative of immunogenic cell death (ICD), in mice expressing non-cleavable ROCK1 (ROCK1nc). Hepatocellular carcinoma (HCC) tumours in ROCK1nc mice had higher grade steatosis, and more neutrophils and CD8+ T cells relative to mice expressing wild-type ROCK1 (ROCK1wt), indicating that spontaneous tumour cell death also was more immunogenic. Since the induction of ICD has been proposed to be tumour-suppressive, the effects of two structurally distinct pharmacological ROCK inhibitors on HCC tumours was examined. Both fasudil and AT13148 significantly decreased tumour numbers and area, but neither treatment resulted in greater numbers of neutrophils or CD8+ T cells to be recruited. In the context of acute DEN-induced liver damage, AT13148 reduced circulating platelet and lymphocyte numbers, and inhibited the recruitment of dendritic, natural killer and CD8+ T cells to livers. These observations indicate that there is an important role for ROCK1 cleavage to limit immunogenic cell death which was not replicated by systemic administration of pharmacological ROCK inhibitors. As a result, adjuvant administration of ROCK inhibitors with cancer therapeutics would be unlikely to result in therapeutic benefit by inducing ICD to increase anti-tumour immune responses.

cancer biology↗

bioRxiv2021

MICAL1 activation by PAK1 mediates actin filament disassembly

The MICAL1 monooxygenase has emerged as an important regulator of filamentous actin (F-actin) structures that contribute to numerous processes including nervous system development, cell morphology, motility, viability and cytokinesis [1-4]. Activating MICAL1 mutations have been linked with autosomal-dominant lateral temporal epilepsy, a genetic syndrome characterized by focal seizures with auditory symptoms [5], emphasizing the need for tight control of MICAL1 activity. F-actin binding to MICAL1 stimulates catalytic activity, resulting in the oxidation of actin methionine residues that promote F-actin disassembly [6, 7]. Although MICAL1 has been shown to be regulated via interactions of the autoinhibitory carboxyl-terminal coiled-coil region [8] with RAB8, RAB10 and RAB35 GTPases [9-12], or Plexin transmembrane receptors [13, 14], a mechanistic link between the RHO GTPase signaling pathways that control actin cytoskeleton dynamics and the regulation of MICAL1 activity had not been established. Here we show that the CDC42 GTPase effector PAK1 serine/threonine kinase associates with and phosphorylates MICAL1 on serine 817 (Ser817) and 960 (Ser960) residues, leading to accelerated F-actin disassembly. Deletion analysis mapped PAK1 binding to the amino-terminal catalytic monooxygenase and calponin domains, distinct from the carboxyl-terminal proteinprotein interaction domain. Stimulation of cells with extracellular ligands including basic fibroblast growth factor (FGF2) led to significant PAK-dependent Ser960 phosphorylation, thus linking extracellular signals to MICAL1 phosphorylation. Moreover, mass spectrometry analysis revealed that co-expression of MICAL1 with CDC42 and active PAK1 resulted in hundreds of proteins increasing their association with MICAL1, including the previously described MICAL1-interacting protein RAB10 [15]. These results provide the first insight into a redox-mediated actin disassembly pathway linking extracellular signals to cytoskeleton regulation via a RHO GTPase family member, and reveal a novel means of communication between RHO and RAB GTPase signaling pathways.

cell biology↗

bioRxiv2020

Global patterns of aegyptism without arbovirus

The worlds most important mosquito vector of viruses, Aedes aegypti, is found around the world in tropical, subtropical and even some temperate locations. While climate change may limit populations of Ae. aegypti in some regions, increasing temperatures will likely expand its territory thus increasing risk of human exposure to arboviruses in places like Europe, Northern Australia and North America, among many others. Most studies of Ae. aegypti biology and virus transmission focus on locations with high endemicity or severe outbreaks of human amplified urban arboviruses, such as dengue, Zika, and chikungunya viruses, but rarely on areas at the margins of endemicity. Our objective in this study is to explore global patterns in the environmental suitability for Ae. aegypti and dengue virus to reveal deviations in the probability of the vector and human disease occurring. We developed a map showing one end of the gradient being higher suitability of Ae. aegypti with low suitability of dengue and the other end of the spectrum being equal and higher environmental suitability for both Ae. aegypti and dengue. The regions of the world with Ae. aegypti environmental suitability and no endemic dengue transmission exhibits a phenomenon we term aegyptism without arbovirus. We then tested what environmental and socioeconomic variables influence this deviation map revealing a significant association with population density, suggesting that locations with lower population density were more likely to have a higher probability of aegyptism without arbovirus. Characterizing regions of the world with established populations of Ae. aegypti but little to no autochthonous transmission of human-amplified arboviruses is an important step in understanding and achieving aegyptism without arbovirus.

ecology↗