Daily Respiratory Research Analysis
Three top studies advanced respiratory science across scales: in situ cryo-electron tomography mapped the native organization of mitochondrial respiratory complexes in cells; a PNAS study uncovered ectopic germinal centers in human and murine nasal turbinates that drive local B-cell immunity to respiratory infection/vaccination; and mechanistic work in Advanced Science identified a Sema3E–Plexin D1–ErbB2 axis, regulated by Furin cleavage, that activates fibroblasts and drives lung fibrosis, offe
Summary
Three top studies advanced respiratory science across scales: in situ cryo-electron tomography mapped the native organization of mitochondrial respiratory complexes in cells; a PNAS study uncovered ectopic germinal centers in human and murine nasal turbinates that drive local B-cell immunity to respiratory infection/vaccination; and mechanistic work in Advanced Science identified a Sema3E–Plexin D1–ErbB2 axis, regulated by Furin cleavage, that activates fibroblasts and drives lung fibrosis, offering therapeutic targets for IPF.
Research Themes
- Native cellular architecture of the mitochondrial respiratory chain
- Nasal turbinate germinal centers and mucosal vaccine immunity
- Fibrogenic signaling (Sema3E–Plexin D1–ErbB2) and therapeutic targets in IPF
Selected Articles
1. In-cell architecture of the mitochondrial respiratory chain.
Using in situ cryo-electron tomography, the authors directly mapped the native structures and spatial organization of mitochondrial respiratory complexes in intact cells. These data inform how electron transport and proton pumping may be coordinated in vivo and provide a structural foundation for understanding respiratory efficiency and disease.
Impact: This study resolves a long-standing debate by visualizing the respiratory chain organization in native cellular context, offering high-resolution insights with broad implications across bioenergetics and disease.
Clinical Implications: A clear map of respiratory complex organization can guide hypotheses for mitochondrial disease mechanisms, biomarkers, and potential interventions that modulate supercomplex assembly or function.
Key Findings
- In situ cryo-electron tomography visualized native structures and organization of major mitochondrial respiratory complexes in cells.
- The data provide direct cellular-context evidence to inform models of electron transfer and proton pumping coordination.
- Establishes a structural framework relevant to respiratory efficiency and mitochondrial disease pathophysiology.
Methodological Strengths
- In situ cryo-electron tomography preserves native cellular context and ultrastructure.
- Direct structural visualization avoids artifacts of biochemical isolation.
Limitations
- Abstracted details of species, cell types, and functional validation are limited in the provided text.
- Static snapshots may not capture dynamic reorganization under varying metabolic states.
Future Directions: Integrate cryo-ET with functional assays and perturbations (e.g., metabolic stress, genetic variants) to link architecture to bioenergetic performance and disease phenotypes.
Mitochondria regenerate adenosine triphosphate (ATP) through oxidative phosphorylation. This process is carried out by five membrane-bound complexes collectively known as the respiratory chain, working in concert to transfer electrons and pump protons. The precise organization of these complexes in native cells is debated. We used in situ cryo-electron tomography to visualize the native structures and organization of several major mitochondrial complexes in
2. Ectopic germinal centers in the nasal turbinates contribute to B cell immunity to intranasal viral infection and vaccination.
Upper airway-targeted influenza infection and immunization elicited robust germinal centers within nasal turbinates, outside classical NALT. These NT germinal centers generated tissue-resident B cells and boosted local antibodies, and steady-state NT GCs were found in mice and healthy humans, positioning the turbinate as a key site for mucosal vaccine design.
Impact: Reveals a previously underappreciated lymphoid niche in the nasal turbinate that supports B-cell memory and antibody production, directly informing next-generation intranasal vaccine strategies.
Clinical Implications: Mucosal vaccines may be optimized by targeting or enhancing nasal turbinate germinal center responses to improve local protection against respiratory viruses.
Key Findings
- Optimized URT-targeted IAV inoculation in mice induced robust germinal center B-cell responses in nasal turbinates outside classical NALT.
- Nasal turbinate germinal centers generated tissue-resident B cells and enhanced local antibody production.
- URT-focused immunization induced significant NT germinal center formation; steady-state NT GCs were detected in mice and healthy humans.
Methodological Strengths
- Combines optimized infection models, immunization, and cross-species (mouse and human) evidence.
- Direct assessment of local B-cell germinal center responses and tissue-resident B-cell generation.
Limitations
- Durability and protective efficacy of NT GC-driven responses against diverse pathogens were not fully quantified.
- Translational vaccine formulations and dosing regimens remain to be defined.
Future Directions: Design intranasal vaccines that specifically enhance nasal turbinate GC responses, and test protection breadth and durability in preclinical and clinical studies.
The nasal mucosa is the first immunologically active site that respiratory viruses encounter and establishing immunity at the initial point of pathogen contact is essential for preventing viral spread. Influenza A virus (IAV) in humans preferentially replicates in the upper respiratory tract (URT) but mouse models of infection result in lower respiratory tract infection. Here, we optimize IAV inoculation to enhance replication in the nasal turbinate (NT) and study local B cell immunity. We demonstrate that URT-targeted IAV infection stimulates robust local B cell responses, including germinal center (GC) B cell formation in the NT, outside of classical nasal-associated lymphoid tissues. NT GC contributes to local tissue-resident B cell generation and enhances local antibody production. Furthermore, URT-focused immunization also induces significant GC formation in the NT. Finally, we detect steady-state GC in the NT of both mice and healthy humans, suggesting continuous immune surveillance triggered by environmental stimuli. These findings highlight the pivotal role of the NT in local and systemic immunity, with important implications for future mucosal vaccines targeting the upper airways.
3. Semaphorin 3E-Plexin D1 Axis Drives Lung Fibrosis through ErbB2-Mediated Fibroblast Activation.
IPF lungs and BLM-fibrotic mouse lungs overexpress Sema3E/Plexin D1; the profibrotic P61-Sema3E isoform (generated by Furin) activates Plexin D1 and ErbB2 phosphorylation to drive fibroblast activation. Genetic or pharmacologic inhibition of Sema3E/Plexin D1/Furin reduces fibroblast activity and mitigates experimental lung fibrosis, nominating a druggable pathway.
Impact: Identifies a specific ligand–receptor–kinase axis (P61-Sema3E–Plexin D1–ErbB2) driving fibroblast pathology in IPF, with convergent evidence from human samples, mechanistic cell work, and in vivo models, opening avenues for targeted anti-fibrotic therapy.
Clinical Implications: Therapeutic strategies inhibiting Furin cleavage of Sema3E, blocking Sema3E–Plexin D1 interaction, or modulating ErbB2 signaling in fibroblasts could be explored as targeted treatments for IPF.
Key Findings
- Sema3E and Plexin D1 are overexpressed in IPF patient lungs and BLM-fibrotic mice; plasma Sema3E inversely correlates with lung function.
- Furin-generated P61-Sema3E activates Plexin D1 and promotes ErbB2 phosphorylation, driving fibroblast activation, proliferation, and migration.
- Sema3E/Plexin D1 knockdown and Furin inhibition reduce fibroblast activity; whole-lung and fibroblast-specific Sema3E loss protect against BLM-induced fibrosis in vivo.
Methodological Strengths
- Integrates human IPF samples, mechanistic in vitro assays, and genetic/pharmacologic interventions in vivo.
- Isoform-specific biology (P61 vs P87) and pathway mapping to ErbB2 signaling.
Limitations
- Translational safety and efficacy of targeting this axis in humans remain untested.
- Potential heterogeneity of Sema3E/Plexin D1 expression across IPF endotypes requires further stratification.
Future Directions: Develop selective inhibitors/antibodies against P61-Sema3E–Plexin D1 and assess anti-fibrotic efficacy, pharmacodynamics, and biomarkers in translational models and early-phase trials.
Idiopathic pulmonary fibrosis (IPF) is characterized by excessive fibroblast recruitment and persistent extracellular matrix deposition at sites of tissue injury, leading to severe morbidity and mortality. However, the precise mechanisms by which fibroblasts contribute to IPF pathogenesis remain poorly understood. The study reveals that Sema3E and its receptor Plexin D1 are significantly overexpressed in the lungs of IPF patients and bleomycin (BLM)-induced lung fibrotic mice. Elevated plasma levels of Sema3E in IPF patients are negatively correlated with lung function. Importantly, Sema3E in IPF lungs predominantly exists as the P61-Sema3E. The knockdown of Sema3E or Plexin D1 effectively inhibits fibroblast activation, proliferation, and migration. Mechanistically, Furin-mediated cleavage of P87-Sema3E into P61-Sema3E drives these pro-fibrotic activities, with P61-Sema3E-PlexinD1 axis promoting fibroblast activation, proliferation, and migration by affecting the phosphorylation of ErbB2, which subsequently activates the ErbB2 pathways. Additionally, Furin inhibition reduces fibroblast activity by decreasing P61-Sema3E production. In vivo, both whole-lung Sema3E knockdown and fibroblast-specific Sema3E knockout confer protection against BLM-induced lung fibrosis. These findings underscore the crucial role of the P61-Sema3E-Plexin D1 axis in IPF pathogenesis and suggest that targeting this pathway may hold promise for the development of novel therapeutic strategies for IPF treatment.