Expression and localization of the cell adhesion molecule SgIGSF during regeneration of the olfactory epithelium in mice

Potential Contribution of Cell Adhesion Molecule 1 to the Binding of SARS-CoV-2 Spike Protein to Mouse Nasal Mucosa

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) first infects the host nasal mucosa, where the viral spike protein binds to angiotensin-converting enzyme 2 (ACE2) on the mucosal cells. This study aimed at searching host cell surface molecules that could contribute to the infection in two views; abundance on host cells and affinity to the spike protein. Since the nasal mucosa is lined by respiratory and olfactory epithelia, and both express an immunoglobulin superfamily member cell adhesion molecule 1 (CADM1), whether CADM1 would participate in the spike protein binding was examined. Immunohistochemistry on the mouse nasal cavity detected CADM1 strongly in the olfactory epithelium at cell-cell contacts and on the apical surface but just faintly in the respiratory epithelium. In contrast, ACE2 was detected in the respiratory, not olfactory, epithelium. When mice were administered intranasally with SARS-CoV-2 S1 spike protein and an anti-CADM1 ectodomain antibody separately, both were detected exclusively on the olfactory, not respiratory, epithelium. Then, the antibody and S1 spike protein were administered intranasally to mice in this order with an interval of 1 h. After 3 h, S1 spike protein was detected as a protein aggregate floating in the nasal cavity. Next, S1 spike protein labeled with fluorescein was added to the monolayer cultures of epithelial cells exogenously expressing ACE2 or CADM1. Quantitative detection of fluorescein bound to the cells revealed that S1 spike protein bound to CADM1 with affinity half as high as to ACE2. Consistently, docking simulation analyses revealed that S1 spike protein could bind to CADM1 three-quarters as strongly as to ACE2 and that the interface of ACE2 was similar in both binding modes. Collectively, intranasal S1 spike protein appeared to prefer to accumulate on the olfactory epithelium, and CADM1 was suggested to contribute to this preference of S1 spike protein based on the molecular abundance and affinity.

ASURA (PHB2) Is Required for Kinetochore Assembly and Subsequent Chromosome Congression

ASURA (PHB2) knockdown has been known to cause premature loss of sister chromatid cohesion, and disrupt the localization of several outer plate proteins to the kinetochore. As a result, cells are arrested at mitotic phase and chromosomes fail to congress to the metaphase plate. In this study, we further clarified the mechanism underlying ASURA function on chromosome congression. Interestingly, ASURA is not specifically localized at the kinetochore during mitotic phase, unlike other kinetochore proteins which construct the kinetochore. Electron microscopy (EM) observation showed that ASURA is required for proper kinetochore formation. By the partial depletion of ASURA, kinetochore maturation is impaired, and kinetochores showing fibrillar balls without a well-defined outer plates are often observed. Moreover, even when the outer plates of kinetochores are constructed, most showed structures stretched and/or distended from the centromere, which resembled premature kinetochores at prometaphase, indicating that the constructed kinetochore plates are less rigid against tension derived from kinetochore microtubule pulling forces. We concluded that ASURA is an essential protein for complete kinetochore development, although ASURA is not being integrated to the kinetochore. These results highlight the uniqueness of ASURA as a kinetochore protein.

Effects of systemic transplantation of adipose tissue-derived stem cells on olfactory epithelium regeneration

OBJECTIVE/HYPOTHESIS

The purpose of the study was to investigate the effect of intravenous adipose tissue-derived stem cell (ADSC) transplantation on olfactory epithelium regeneration following transection of the olfactory nerve in rats.

STUDY DESIGN

This was a experimental study using primary cultures of mesenchymal stem cells derived from animal adipose tissue with histological analysis of animal olfactory tissue.

METHODS

All rats underwent unilateral transection of the olfactory nerve to induce degeneration of olfactory epithelium, and then were observed for regeneration according to time sequences. ADSCs were cultivated from neck adipose tissue of rats, and systemically injected into the experimental group. The control group was injected with phosphate buffered solution, instead of ADSCs. After 30 days, regeneration of olfactory epithelium was observed with olfactory marker protein (OMP) and proliferating cell nuclear antigen. To observe the characteristics of the transplanted ADSCs, olfactory epithelium was stained with von Willebrant factor and OMP.

RESULTS

After olfactory nerve transection, mature olfactory cells disappeared in 5 days, but gradually regained their thickness with increased cell numbers at approximately 10 to 15 days. By 30 days post-transection, the thickness and cellular composition of epithelium was almost restored to baseline levels pretransection. However, OMP expressions remained decreased compared with day 0 or 3. Systemically injected ADSCs were transplanted into the olfactory epithelium and survived beyond 4 weeks. The ADSCs promoted regeneration of olfactory epithelium in the animal model and differentiated into olfactory receptor neurons and endothelial cells.

CONCLUSIONS

Our findings suggest the feasibility of ADSC transplantation as a treatment for head trauma-related olfactory dysfunction.

Expression, localization, and binding activity of the ezrin/radixin/moesin proteins in the mouse testis

The ezrin, radixin, and moesin (ERM) proteins represent a family of adaptor proteins linking transmembrane proteins to the cytoskeleton. The seminiferous epithelium undergoes extensive changes in cellular composition, location, and shape, implicating roles of the membrane-cytoskeleton interaction. It remains unknown, however, whether the ERM proteins are expressed and play significant roles in the testis. In the present study, we examined the spatiotemporal expression of ERM proteins in the mouse testis by Western blotting and immunohistochemistry. Ezrin immunoreactivity was demonstrated in the cytoplasm of steps 15 and 16 spermatids from 5 weeks postpartum through adulthood, whereas radixin immunoreactivity was in the apical cytoplasm of Sertoli cells from 1 week through 2 weeks postpartum. No immunoreactivity for moesin was detected at any age. Immunoprecipitation demonstrated that ezrin was bound to the cytoskeletal component actin, whereas radixin was bound to both actin and tubulin. Of the transmembrane proteins known to interact with ERM proteins, only cystic fibrosis transmembrane conductance regulator, a chloride transporter, was bound to ezrin in elongated spermatids. These results suggest that ezrin is involved in spermiogenesis whereas radixin is involved in the maturation of Sertoli cells, through interaction with different sets of membrane proteins and cytoskeletal components.

The adhesion molecule Necl-3/SynCAM-2 localizes to myelinated axons, binds to oligodendrocytes and promotes cell adhesion

Background

Cell adhesion molecules are plasma membrane proteins specialized in cell-cell recognition and adhesion. Two related adhesion molecules, Necl-1 and Necl-2/SynCAM, were recently described and shown to fulfill important functions in the central nervous system. The purpose of the work was to investigate the distribution, and the properties of Necl-3/SynCAM-2, a previously uncharacterized member of the Necl family with which it shares a conserved modular organization and extensive sequence homology.

Results

We show that Necl-3/SynCAM-2 is a plasma membrane protein that accumulates in several tissues, including those of the central and peripheral nervous system. There, Necl-3/SynCAM-2 is expressed in ependymal cells and in myelinated axons, and sits at the interface between the axon shaft and the myelin sheath. Several independent assays demonstrate that Necl-3/SynCAM-2 functionally and selectively interacts with oligodendrocytes. We finally prove that Necl-3/SynCAM-2 is a bona fide adhesion molecule that engages in homo- and heterophilic interactions with the other Necl family members, leading to cell aggregation.

Conclusion

Collectively, our manuscripts and the works on Necl-1 and SynCAM/Necl-2 reveal a complex set of interactions engaged in by the Necl proteins in the nervous system. Our work also support the notion that the family of Necl proteins fulfils key adhesion and recognition functions in the nervous system, in particular between different cell types.