Biology subjects

Myung, K.

Publications and source records attributed to Myung, K..

6 recordsLinked to original sources

bioRxiv2025

Distinct modes of dopamine modulation on striatopallidal synaptic transmission

Dopamine (DA) affects voluntary movement by modulating basal ganglia function. In the classical model, DA depletion leads to overactivity of the indirect pathway and excessively inhibits the thalamus, resulting in hypokinesia. The contribution of DA on striatopallidal synapses, an initial hub in the indirect pathway connecting the striatum to the external globus pallidus (GPe), remains poorly understood because of the sparse DA innervation. Here, we combine optogenetic projection targeting, whole cell patch clamp recordings in acute brain slices from mice, and computational modeling to overcome this limitation. We show that DA activates D2R receptors (D2Rs) and D4 receptors (D4Rs) differentially in distinct GPe subregions. In a pinwheel-like fashion, dorsolateral and ventromedial GPe expresses high levels of D2Rs, which exert presynaptic inhibition, while in dorsomedial and ventrolateral GPe D4Rs cause postsynaptic inhibition. DA depletion by 6-OHDA (6-hydroxydopamine) reverses the region- specific effect of DA, shifting it in the opposite direction and contributing to hypokinesia. These findings reveal the mechanism by which the different modality information conveyed spatially through the indirect pathway is differentially modulated by DA at striatopallidal synapses.

neuroscience↗

bioRxiv2024

Hidden route of protein damage through confined oxygen gas

Oxidative modifications can severely impair protein structure, fold, and function, closely linked to human aging and diseases. Conventional oxidation pathways typically involve the free diffusion of reactive oxygen species (ROS), followed by chemical attacks on the protein surface. Here, we report a hidden route of protein oxidative damage, which we refer to as O2-confinement oxidation pathway. This pathway starts with the initial trapping of dissolved molecular oxygen (O2) within protein cavity spaces, followed by interaction with photosensitizing tryptophan residues. The trapped O2 is then converted to singlet oxygen (1O2), a powerful ROS, through spin-flip electron transfer mechanism under blue light. The generated 1O2 within the protein ultimately attacks the protein core residues through constrained diffusion, accelerating the oxidative damage. This alternative photooxidation pathway through the initial O2 trapping would bypass the antioxidant defense systems which target freely-diffusing ROS, constituting an additional layer of protein oxidative damage in cells and tissues.

biochemistry↗

bioRxiv2023

Polyubiquitinated PCNA promotes alternative lengthening of telomeres by inducing break-induced replication

Replication stresses are the major source of break-induced replication (BIR). Here, we show that in alternative lengthening of telomeres (ALT) cells, replication stress-induced polyubiquitinated PCNA (polyUb-PCNA) triggers BIR at telomeres and the common fragile site (CFS). Consistently, depleting RAD18, a PCNA ubiquitinating enzyme, reduces the occurrence of ALT-associated PML bodies (APBs) and mitotic DNA synthesis at telomeres and CFS, both of which are mediated by BIR. In contrast, inhibiting USP1, an Ub-PCNA deubiquitinating enzyme, results in an increase in the above phenotypes in a RAD18- and UBC13 (the PCNA polyubiquitinating enzyme)-dependent manner. Furthermore, deficiency of ATAD5, which facilitates USP1 activity and unloads PCNAs, augments recombination-associated phenotypes. Mechanistically, telomeric polyUb-PCNA accumulates SLX4, a nuclease scaffold, at telomeres through its ubiquitin-binding domain and increases telomere damage. Consistently, APB increase induced by Ub-PCNA depends on SLX4 and SLX4-associated nucleases. Taken together, our results identified the polyUb-PCNA-SLX4 axis as a trigger for directing BIR.

cell biology↗

bioRxiv2021

MSH2-MSH3 promotes DNA end resection during HR and blocks TMEJ through interaction with SMARCAD1 and EXO1

DNA double strand break (DSB) repair by Homologous recombination (HR) is initiated by the end resection, a process during which 3 ssDNA overhangs are generated by the nucleolytic degradation. The extent of DNA end resection determines the choice of the DSB repair pathway. The role of several proteins including nucleases for end resection has been studied in detail. However, it is still unclear how the initial, nicked DNA generated by MRE11-RAD50-NBS1 is recognized and how subsequent proteins including EXO1 are recruited to DSB sites to facilitate extensive end resection. We found that the MutS{beta} (MSH2-MSH3) mismatch repair (MMR) complex is recruited to DSB sites by recognizing the initial nicked DNA at DSB sites through the interaction with the chromatin remodeling protein SMARCAD1. MSH2-MSH3 at DSB sites helps to recruit EXO1 for long-range resection and enhances its enzymatic activity. MSH2-MSH3 furthermore inhibits the access of DNA polymerase {theta} (POLQ), which promotes polymerase theta-mediated end-joining (TMEJ) of DSB. Collectively, our data show a direct role for MSH2-MSH3 in the initial stages of DSB repair by promoting end resection and influencing DSB repair pathway by favoring HR over TMEJ. Our findings extend the importance of MMR in DSB repair beyond established role in rejecting the invasion of sequences not perfectly homologous to template DNA during late-stage HR.

molecular biology↗

bioRxiv2020

GJA1 Depletion Causes Ciliary Defects by Affecting Rab11 Trafficking to the Ciliary Base

The gap junction complex functions as a transport channel across the membrane. Among gap junction subunits, gap junction protein 1 (GJA1) is the most commonly expressed subunit. A recent study showed that GJA1 is necessary for the maintenance of motile cilia; however, the molecular mechanism and function of GJA1 in ciliogenesis remain unknown. Here, we examined the functions of GJA1 during ciliogenesis in human retinal pigment epithelium-1 and Xenopus laevis embryonic multiciliated-cells. GJA1 localizes to the motile ciliary axonemes or pericentriolar regions beneath the primary cilium. GJA1 depletion caused malformation of both the primary cilium and motile cilia. Further study revealed that GJA1 depletion affected several ciliary proteins such as BBS4, CP110, and Rab11 in the pericentriolar region and basal body. Interestingly, CP110 removal from the mother centriole was significantly reduced by GJA1 depletion. Importantly, Rab11, a key regulator during ciliogenesis, was immunoprecipitated with GJA1, and GJA1 knockdown caused the mislocalization of Rab11. These findings suggest that GJA1 regulates ciliogenesis by interacting with the Rab11-Rab8 ciliary trafficking pathway.

cell biology↗

bioRxiv2020

High-throughput phenotypic characterization of zebrafish CRISPR mutants of DNA repair genes

A systematic knowledge of the roles of DNA repair genes at the level of the organism has been limited due to the lack of appropriate experimental techniques. Here, we generated zebrafish loss-of-function mutants for 32 DNA repair and replication genes through multiplexed CRISPR/Cas9-mediated mutagenesis. High-throughput phenotypic characterization of our mutant collection revealed that three genes (atad5a, ddb1, pcna) are essential for proper embryonic development and hematopoiesis; seven genes (apex1, atrip, ino80, mre11a, shfm1, telo2, wrn) are required for growth and development during juvenile stage and six genes (blm, brca2, fanci, rad51, rad54l, rtel1) play critical roles in sex development. Furthermore, mutation in six genes (atad5a, brca2, polk, rad51, shfm1, xrcc1) displayed hypersensitivity to DNA damage agents. Further characterization of atad5a-/- mutants demonstrate that Atad5a is required for normal brain development and hematopoiesis. Our zebrafish mutant collection provides a unique resource for understanding of the roles of DNA repair genes at the organismal level.

developmental biology↗