Biology subjects

Hsu, P.-H.

Publications and source records attributed to Hsu, P.-H..

6 recordsLinked to original sources

bioRxiv2025

MEX3A control of mitochondrial fitness is essential for ovarian clear cell carcinoma tumorigenesis and liver metastasis

Ovarian cancer (OC) is highly metastatic and chemoresistant. Due to heterogeneity among OC subtypes, the mechanisms underlying OC malignancy and metastasis remain largely unknown. Ovarian clear cell carcinoma (OCCC) accounts for 5-25% of OC and its incidence rate is rising. Liver metastasis is particularly high in OCCC patients and leads to significantly reduced median survival. Why OCCC metastasizes to liver at such high frequency remains elusive. We previously identified MEX3A as a key factor that promotes OCCC tumorigenesis in part by circumventing p53-mediated ferroptosis. Here, we report that MEX3A control of mitochondrial fitness, which occurs independently of p53, is essential for OCCC primary tumor growth and liver metastasis. MEX3A depletion resulted in chronic mitochondrial fragmentation and accumulation of non-functional mitochondria. MEX3A-depleted cells had decreased mitochondrial membrane potential, increased superoxide and decreased NAD+/NADH ratio, resulting in inhibition of oxidative phosphorylation (OXPHOS) and decreased ATP levels. In an environment enriched with mitophagy stressors, such as the liver, MEX3A-depleted OCCC cells had greatly reduced survival due to failure to recover from mitophagy. Consistent with these observations, MEX3A knockdown greatly reduced liver metastasis. Together, these data demonstrate that MEX3A-mediated mitochondrial fitness is a major factor underlying its p53-independent promotion of OCCC tumorigenesis and liver metastasis. Thus, targeting MEX3A will be a promising strategy to inhibit OCCC progression. Statement of significanceUnexpected effects of MEX3A on mitochondrial fitness indicate that the need for high MEX3A expression is an OCCC vulnerability that can be exploited to uncover new treatment strategies.

cancer biology↗

bioRxiv2024

Naa10 regulates hippocampal neurite outgrowth via Btbd3 N-α-acetylation-mediated actin dynamics

Protein N--acetylation is widespread in eukaryotes, yet its neuronal role remains unclear. Mutations in human N--acetyltransferase 10 (NAA10) lead to developmental defects affecting brain function, such as intellectual disability and autism. We found that hippocampal CA1-specific Naa10-knockout mice exhibit anxiety and reduced hippocampal dendritic complexity. Mechanistically, Naa10 promotes neurite outgrowth by acetylating BTB/POZ domain-containing protein 3 (Btbd3), crucial for the interaction of Btbd3 with filamentous actin (F-actin)-capping protein subunit beta (CapZb). Disrupting the Btbd3/CapZb interaction, either through Naa10 knockout or by expressing an N--acetylation-defective Btbd3 mutant, diminishes CapZb binding to F-actin and reduces neurite outgrowth. Moreover, cytochalasin D, a compound like CapZb in capping the barbed end of F-actin, rescues the Naa10 knockout-induced neurite reduction in hippocampal primary neurons. These findings unveil the role of Naa10 in enhancing hippocampal neurite outgrowth through the Btbd3-CapZb-F-actin axis, shedding light on potential mechanisms underlying X-linked Ogden syndrome resulting from human NAA10 mutations. eTOCChou et al. demonstrate that Naa10 promotes neurite outgrowth by N-acetylating Btbd3, facilitating the binding of the filamentous actin capping protein subunit beta (CapZb) to F-actin. Their study establishes a connection between protein N--acetylation and neuronal function, providing insight into the mechanism underlying brain disorders associated with human NAA10 mutations. HIGHLIGHTSO_LIHippocampal CA1-specific Naa10 KO leads to anxiety C_LIO_LIHippocampal CA1-specific Naa10 KO reduces hippocampal dendritic complexity C_LIO_LINaa10 promotes neurite outgrowth by N-acetylating Btbd3 C_LIO_LINaa10-mediated Btbd3 N--acetylation promotes CapZb binding to F-actin C_LI Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=200 SRC="FIGDIR/small/583166v1_ufig1.gif" ALT="Figure 1"> View larger version (43K): org.highwire.dtl.DTLVardef@180da41org.highwire.dtl.DTLVardef@7921c6org.highwire.dtl.DTLVardef@9859b0org.highwire.dtl.DTLVardef@28687c_HPS_FORMAT_FIGEXP M_FIG C_FIG

developmental biology↗

bioRxiv2022

BMAL1 and MEX3A co-regulate intestinal stem cell succession

Chemotherapeutic agents, such as 5-fluorouracil (5-FU), often induce intestinal mucositis due to toxicity to rapidly dividing intestinal stem cells (ISCs). Drug delivery at different times of day can alter 5-FU toxicity; however, the underlying biology is unclear. We found that homeostasis and succession between two ISC types, fast proliferating Lgr5+ crypt base columnar (CBC) cells and stress-resistant +4 cells (Bmi1+), are controlled by the circadian clock transcription factor BMAL1 and the BMAL1-regulated RNA-binding protein MEX3A via both direct transcriptional regulation and post-transcriptional control of Lgr5 mRNA stability. Bmal1 knockout in Lgr5+ CBCs reduced MEX3A expression and CBC numbers but increased Bmi1 expression in the crypts. Timing 5-FU delivery when crypt cells had low Lgr5 but peak level of Bmi1 protected ISCs from apoptosis. Together, these findings identify a novel role of BMAL1 in ISC homeostasis and provide a biological explanation for chronotherapeutic chemoprotection.

cell biology↗

bioRxiv2020

METTL5, an 18S rRNA-specific m6A methyltransferase, modulates expression of stress response genes

RNA N6-methyladenosine (m6A) modification is present in different RNA molecules, including protein-coding mRNAs and non-coding RNAs such as ribosomal RNAs (rRNAs). Previous studies identified m6A in both the 18S and 28S rRNAs, but the roles of these methylation events are poorly understood due to the lack of knowledge of the responsible methyltransferases. Here, we report that mammalian METTL5, a member of a highly conserved methyltransferase family, specifically methylates adenosine 1832 (A1832) in the 18S rRNA in vivo and in vitro. We identify TRMT112 as a near stoichiometric partner of METTL5 important for the enzymatic activity of METTL5. By mapping the positions of translating ribosomes (Ribo-seq), we found translation of multiple stress response-related mRNAs, including Atf4 mRNA, is selectively reduced in the Mettl5 knockout (KO) mouse B16 melanoma cells. Atf4 is a key transcription factor that mediates the Integrated Stress Response (ISR), as exemplified by the Endoplasmic Reticulum (ER) stress. Consistently, transcription of ISR effector genes is reduced in Mettl5 KO cells during ER stress, suggesting a compromised ISR. Our findings reveal a new mechanism that regulates expression of stress response genes and suggest that chemical modifications of ribosomal RNAs may play a key role in selectively impacting translation and possibly ISR.

biochemistry↗

bioRxiv2019

Interplay between Desmoglein2 and hypoxia controls intravasation and circulating tumor cell clustering in breast cancer metastasis

Metastasis is the major cause of cancer death. An increased level of circulating tumor cells (CTCs), metastatic cancer cells that have intravasated into the circulatory system, is particularly associated with colonization of distant organs and poor prognosis. However, the key factors required for tumor cell dissemination and colonization remain elusive. We found that high expression of Desmoglein2 (DSG2), a component of desmosome-mediated intercellular adhesion complexes, promoted tumor growth, increased the prevalence of CTC clusters and facilitated distant organ colonization. The dynamic regulation of DSG2 by hypoxia was key to this process as downregulation of DSG2 in hypoxic regions of primary tumors led to elevated epithelial-mesenchymal transition (EMT) gene expression, allowing cells to detach from the primary tumor and undergo intravasation. Subsequent derepression of DSG2 after intravasation and release of hypoxic stress was associated with an increased ability to colonize distant organs. This dynamic regulation of DSG2 was mediated by Hypoxia-Induced Factor1 (HIF1). In contrast to its more widely observed function to promote expression of hypoxia-inducible genes, HIF1 repressed DSG2 by recruitment of the Polycomb Repressive Complex 2 components, EZH2 and SUZ12, to the DSG2 promoter in hypoxic cells. Consistent with our experimental data, DSG2 expression level correlated with poor prognosis and recurrence risk in breast cancer patients. Together, these results demonstrated the importance of DSG2 expression in metastasis and revealed a new mechanism by which hypoxia drives metastasis. Significance StatementDuring metastasis, hypoxia is a major force driving primary tumor cells to disseminate into the circulatory system. The key factors that promote circulating tumor cells (CTC) dissemination and allow them to successfully colonize distal sites are still incompletely known. We found that downregulation of DSG2 in hypoxic tumor allowed single tumor cell dissemination while DSG2 expressing tumors generated more CTC clusters. Re-induction of DSG2 expression in single CTCs may contribute to CTC survival and colonization in distant organs. These findings highlight the importance of DSG2 in breast cancer progression and metastasis.

cancer biology↗

bioRxiv2019

Differential Effects of SUMO1/2 on Circadian Protein PER2 Stability and Function

Posttranslational modification (PTM) of core circadian clock proteins, including Period2 (PER2), is required for proper circadian regulation. PER2 function is regulated by casein kinase 1 (CK1)-mediated phosphorylation and ubiquitination but little is known about other PER2 PTMs or their interaction with PER2 phosphorylation. We found that PER2 can be SUMOylated by both SUMO1 and SUMO2; however, SUMO1 versus SUMO2 conjugation had different effects on PER2 turnover and transcriptional suppressor function. SUMO2 conjugation facilitated PER2-{beta}-TrCP interaction leading to PER2 proteasomal degradation. In contrast, SUMO1 conjugation, mediated by E3 SUMO-protein ligase RanBP2, enhanced CK1-mediated PER2S662 phosphorylation and increased PER2 transcriptional suppressor function. PER2 K736 was critical for both SUMO1- and SUMO2-conjugation. A PER2K736R mutation was sufficient to alter circadian periodicity and reduce PER2-mediated transcriptional suppression. Together, our data revealed SUMO1 versus SUMO2 conjugation acts as an upstream determinant of PER2 phosphorylation and thereby affects the circadian regulatory system and circadian periodicity.

molecular biology↗