Biology subjects

Lee, D.-K.

Publications and source records attributed to Lee, D.-K..

4 recordsLinked to original sources

bioRxiv2024

Phospholipase C β4 promotes RANKL-dependent osteoclastogenesis by interacting with MKK3 and p38 MAPK

Phospholipase C beta (PLC{beta}) exerts diverse biological processes, including inflammatory responses and neurogenesis; however, its role in bone cell function is largely unknown. Among the PLC{beta} isoforms ({beta}1-{beta}4), we found that PLC{beta}4 was most highly upregulated during osteoclastogenesis. In this study, we used global knockout and osteoclast lineage-specific PLC{beta}4 conditional knockout (LysM-PLC{beta}4-/-) mice and demonstrated that PLC{beta}4 is a crucial regulator of receptor activator of nuclear factor {kappa}B ligand (RANKL)-induced osteoclast differentiation. Deletion of PLC{beta}4, both globally and in the osteoclast lineage, resulted in a significant reduction in osteoclast formation and the downregulation of osteoclast marker genes. Importantly, LysM-PLC{beta}4-/- male mice exhibited greater bone mass and a lower number of osteoclasts in vivo than their wild-type littermates, without altering osteoblast function. Mechanistically, we found that PLC{beta}4 forms a complex with p38 mitogen-activated protein kinase (MAPK) and MAPK kinase 3 (MKK3) in response to RANKL, thereby modulating p38 activation. An immunofluorescence assay further confirmed the colocalization of PLC{beta}4 with p38 after RANKL exposure. Moreover, p38 activation rescued the impaired osteoclast formation and restored the reduced p38 phosphorylation due to PLC{beta}4 deficiency. Thus, our findings reveal that PLC{beta}4 controls osteoclastogenesis via the RANKL-dependent MKK3-p38 MAPK pathway, and PLC{beta}4 may be a potential therapeutic candidate for bone diseases such as osteoporosis.

cell biology↗

bioRxiv2024

Dimeric R25CPTH(1-34) Activates the Parathyroid Hormone-1 Receptor in vitro and Stimulates Bone Formation in Osteoporotic Female Mice

Osteoporosis, characterized by reduced bone density and strength, increases fracture risk, pain, and limits mobility. Established therapies of Parathyroid hormone (PTH) analogs effectively promote bone formation and reduce fractures in severe osteoporosis, but their use is limited by potential adverse effects. In the pursuit of safer osteoporosis treatments, we investigated R25CPTH, a PTH variant wherein the native arginine at position 25 is substituted by cysteine. These studies were prompted by our finding of high bone mineral density in a hypoparathyroidism patient with the R25C homozygous mutation, and we explored its effects on PTH type-1 receptor (PTH1R) signaling in cells and bone metabolism in mice. Our findings indicate that R25CPTH(1-84) forms dimers both intracellularly and extracellularly, and the synthetic dimeric peptide, R25CPTH(1-34), exhibits altered activity in PTH1R-mediated cAMP response. Upon a single injection in mice, dimeric R25CPTH(1-34) induced acute calcemic and phosphaturic responses comparable to PTH(1-34). Furthermore, repeated daily injections increased calvarial bone thickness in intact mice and improved trabecular and cortical bone parameters in ovariectomized (OVX) mice, akin to PTH(1-34). The overall results reveal a capacity of a dimeric PTH peptide ligand to activate the PTH1R in vitro and in vivo as PTH, suggesting a potential path of therapeutic PTH analog development.

genomics↗

bioRxiv2022

Transcriptional control of motor pool formation and motor circuit connectivity by the LIM-HD protein Isl2

The fidelity of motor control requires the precise positional arrangement of motor pools and the establishment of synaptic connections between these pools. In the developing spinal cord, motor nerves project to specific target muscles and receive proprioceptive input from the muscles via the sensorimotor circuit. LIM-homeodomain transcription factors are known to successively restrict specific motor neuronal fates during neural development; however, it remains unclear to what extent they contribute to limb-based motor pools and locomotor circuits. Here, we showed in mice that deletion of Isl2 resulted in scattered motor pools, primarily in the median motor column and lateral LMC (LMCl) populations, and lacked Pea3 expression in the hindlimb motor pools, accompanied by reduced terminal axon branching and disorganized neuromuscular junctions. Transcriptomic analysis of Isl2- deficient spinal cords revealed that a variety of genes involved in motor neuron differentiation, axon development, and synapse organization were downregulated in hindlimb motor pools. Moreover, the loss of Isl2 impaired sensorimotor connectivity and hindlimb locomotion. Together, our studies indicate that Isl2 plays a critical role in organizing motor pool position and sensorimotor circuits in hindlimb motor pools.

neuroscience↗

bioRxiv2019

Magnetic-Alignment of Polymer Nanodiscs Probed by Solid-State NMR Spectroscopy

The ability of amphipathic polymers to self-assemble with lipids and form nanodiscs has been a boon for the field of functional reconstitution of membrane proteins. In a field dominated by detergent micelles, a unique feature of polymer nanodiscs is their much-desired ability to align in the presence of an external magnetic field. Magnetic alignment facilitates the application of solid-state NMR spectroscopy and aids in the measurement of residual dipolar couplings (RDCs) via well-established solution NMR spectroscopy. In this study, we comprehensively investigate the magnetic-alignment properties of SMA-QA polymer based nanodiscs by using 31P and 14N solid-state NMR experiments under static conditions. The results reported herein demonstrate the spontaneous magnetic-alignment of large-size ([≥] 20 nm diameter) SMA-QA nanodiscs (also called as macro-nanodiscs) with the lipid-bilayer-normal perpendicular to the magnetic field direction. Consequently, the orientation of macro-nanodiscs are further shown to flip their alignment axis parallel to the magnetic field direction upon the addition of a paramagnetic lanthanide salt. These results demonstrate the use of SMA-QA polymer nanodiscs for solid-state NMR applications including structural studies on membrane proteins.

biophysics↗