Kyeong-Man Kim

Kyeong-Man Kim. Biomolecules & Therapeutics 2026;34:1283-98. https://doi.org/10.4062/biomolther.2026.132

African swine fever virus (ASFV) research commonly relies on primary porcine alveolar macrophages (PAMs), whose limited availability and variability hinder standardized virus isolation and propagation. This study aimed to establish a continuous cell line highly susceptible to genotype II ASFV and characterize phenotypic and genomic changes during serial passage. Thirty COS-1-derived clones were screened after infection with Korea/Pig/PAJU1/2019 using quantitative real-time polymerase chain reaction, immunofluorescence, and hemadsorption assays. Selected clones underwent serial passage, and viruses from passages 5 and 10 in the most susceptible clone were analyzed by whole-genome sequencing. K-C4 supported stable ASFV replication, with a mean viral genome level of 8.80 ± 0.55 log₁₀ copies/mL, compared with 7.38 ± 0.90 log₁₀ copies/mL in PAMs. Productive infection was confirmed by p72-specific immunofluorescence. The parental and passage 1 viruses retained hemadsorption, whereas the passage 5 virus lacked detectable hemadsorption despite continued replication, and hemadsorption reappeared by passage 10. Whole-genome analysis identified passage-associated deletions of differing extent within EP402R, encoding the hemadsorption-associated CD2-like viral protein (CD2v), which corresponded with the hemadsorption phenotype at each passage. These findings establish K-C4 as a highly permissive platform for genotype II ASFV propagation and characterization while emphasizing the need to monitor phenotypic and genomic stability during serial passage.

Δ9-Tetrahydrocannabinol (THC), the principal psychoactive constituent of Cannabis sativa, exerts its central effects predominantly through the cannabinoid CB1 receptor (CB1R). However, molecular mechanisms underlying THC actions beyond canonical CB1R signaling have been suggested but remain incompletely defined. Systematic screening of 14 structurally diverse cannabinoid compounds identified THC as a direct agonist at the dopamine D2 receptor (D2R). THC selectively activated ERK signaling through D2-like receptors, directly bound D2R with submicromolar affinity, and functioned as a G protein–biased agonist that engages Gi/o-dependent signaling without recruiting arrestin pathways. Mechanistically, this biased signaling enabled D2R to transactivate EGFR via a cascade involving Src, PI3K, and PKC. Activated EGFR, in turn, sustained phosphorylation of Src and PKCβII, establishing a positive feed-forward loop that prolongs ERK activation. These findings demonstrate that THC directly engages D2R in parallel with the canonical CB1R-mediated disinhibition of dopaminergic neurons, providing a comprehensive molecular framework that links cannabis exposure to aberrant dopaminergic signaling. By acting as a Gi/o-biased partial agonist at D2R, THC is poised to both modulate canonical dopaminergic transmission and initiate a distinct EGFR-dependent signaling program. This dual mechanism offers a revised view of THC pharmacology and its potential contribution to neuropsychiatric effects associated with cannabis exposure.

Lei Huang, Mengling Wang, Dooti Kundu, Suresh Paudel, Lulu Peng, Xinru Xian, Choon-Gon Jang and Kyeong-Man Kim. Biomolecules & Therapeutics 2026;34:556-64. https://doi.org/10.4062/biomolther.2025.255

G protein-coupled receptors (GPCRs) form the largest family of cell-surface signaling proteins and remain the most exploited drug targets. Their regulation depends on desensitization, the attenuation of receptor responsiveness following sustained or repeated stimulation. The canonical framework, validated for rhodopsin and the β2-adrenergic receptor, describes desensitization as GRK-mediated receptor phosphorylation, arrestin recruitment, and steric occlusion of G protein coupling. This receptor-centric view has been supported primarily by time-course assays of second messenger generation, which capture rapid, reversible attenuation at the plasma membrane. Recent studies, however, reveal a receptor-distal program in which arrestin deubiquitination, regulated by EGFR–Akt–USP33 signaling, converts arrestin into a Gβγ-sequestering state and drives nuclear redistribution of signaling components. This perspective has been advanced through washout–rechallenge assays (pulse‑chase‑pulse), which demonstrate diminished responsiveness upon repeated stimulation even after receptor recovery. Integrating these complementary approaches, we propose a two-level framework for GPCR desensitization. Level 1 (proximal) reflects rapid receptor-core uncoupling, suited to transient stimulation. Level 2 (distal) reflects slower, trafficking-dependent redistribution of signaling machinery, producing more durable attenuation. This layered model reconciles divergent experimental findings, explains receptor subtype diversity, and highlights how desensitization extends beyond receptor blockade to spatial reorganization of signaling components. By linking methodological differences to mechanistic insights, this framework provides a unified view of GPCR desensitization. It informs future directions in biased agonism, acute tolerance, and the design of therapeutics with tailored desensitization profiles.

Upon activation of certain G protein-coupled receptors, Mdm2 promotes the ubiquitination of both GRK2 and arrestin3. Similar to arrestin3, GRK2 ubiquitination was associated with its endocytic activity and proteasomal degradation. Ubiquitination of GRK2 was essential for arrestin3 ubiquitination, and vice versa. Cellular components involved in arrestin3 ubiquitination, including Gβγ, clathrin, and 14-3-3η, were also necessary for GRK2 ubiquitination. Additionally, the arrestin-biased signaling pathway contributed to the ubiquitination of both GRK2 and arrestin3. By employing Mdm2-knockdown cells alongside GRK2 and arrestin3 mutants deficient in ubiquitination sites, as well as receptors lacking phosphorylation sites, we established that the ubiquitinated forms of GRK2 and arrestin3 facilitate clathrin-dependent endocytosis, whereas non-ubiquitinated GRK2 and arrestin3 are responsible for caveolar and a distinct third endocytic pathway, respectively. In the context of clathrin-mediated endocytosis, arrestin3’s interaction with clathrin and GRK2’s interaction with the β2-adaptin subunit of adaptor protein complex 2 were critical. These findings suggest that GRK2 and arrestin3 ubiquitination are mutually dependent, with their ubiquitination states determining their roles in distinct endocytic pathways.

Upon activation of certain G protein-coupled receptors, Mdm2 promotes the ubiquitination of both GRK2 and arrestin3. Similar to arrestin3, GRK2 ubiquitination was associated with its endocytic activity and proteasomal degradation. Ubiquitination of GRK2 was essential for arrestin3 ubiquitination, and vice versa. Cellular components involved in arrestin3 ubiquitination, including Gβγ, clathrin, and 14-3-3η, were also necessary for GRK2 ubiquitination. Additionally, the arrestin-biased signaling pathway contributed to the ubiquitination of both GRK2 and arrestin3. Using Mdm2-knockdown cells, GRK2 and arrestin3 mutants lacking ubiquitination sites, and receptors deficient in phosphorylation sites, we demonstrated that ubiquitinated GRK2/arrestin3, non-ubiquitinated GRK2, and non-ubiquitinated arrestin3 mediate clathrin-dependent, caveolar, and a third distinct endocytic pathway, respectively. In the context of clathrin-mediated endocytosis, arrestin3’s interaction with clathrin and GRK2’s interaction with the β2-adaptin subunit of adaptor protein complex 2 were critical. These findings suggest that GRK2 and arrestin3 ubiquitination are mutually dependent, with their ubiquitination states determining their roles in distinct endocytic pathways.