Myeloid-biased HSC require Semaphorin 4A from the bone marrow niche for self-renewal under stress and life-long persistence

Tissue stem cells are hierarchically organized. Those that are most primitive serve as key drivers of regenerative response but the signals that selectively preserve their functional integrity are largely unknown. Here, we identify a secreted factor, Semaphorin 4A (Sema4A), as a specific regulator of myeloid-biased hematopoietic stem cells (myHSC), which are positioned at the top of the HSC hierarchy. Lack of Sema4A leads to exaggerated myHSC (but not downstream balanced HSC) proliferation after acute inflammatory stress, indicating that Sema4A enforces myHSC quiescence. Strikingly, aged Sema4A knock-out myHSC expand but almost completely lose reconstitution capacity. The effect of Sema4A is non cell-autonomous, since upon transplantation into Sema4A-deficient environment, wild-type myHSC excessively proliferate but fail to engraft long-term. Sema4A constrains inflammatory signaling in myHSC and acts via a surface receptor Plexin-D1. Our data support a model whereby the most primitive tissue stem cells critically rely on a dedicated signal from the niche for self-renewal and life-long persistence.

Molecular dynamics simulations of the delta and omicron SARS-CoV-2 spike – ACE2 complexes reveal distinct changes between both variants

SARS-CoV-2, the virus which causes the COVID-19 pandemic, changes frequently through the ap-pearance of mutations constantly leading to new variants. However, only few variants evolve as dominating and will be considered as “Variants of Concern” (VOCs) by the world health organization (WHO). At the end of 2020 the alpha (B.1.1.7) variant appeared in the United Kingdom and domi-nated the pandemic situation until mid of 2021 when it was substituted by the delta variant (B.1.617.2) that first appeared in India as predominant variant. At the end of 2021, SARS-CoV-2 omi-cron (B.1.1.529) evolved as the dominating variant. Here, we use in silico modeling and molecular dynamics (MD) simulations of the receptor-binding domain of the viral spike protein and the host cell surface receptor ACE2 to analyze and compare the interaction pattern between the wild type, delta and omicron variants. We identified residue 493 in delta (glutamine) and omicron (arginine) with altered binding properties towards ACE2.

Cell surface receptor kinase FERONIA linked to nutrient sensor TORC1 signaling controls root hair growth at low temperature in Arabidopsis thaliana

Root hairs (RH) are excellent model systems for studying cell size regulation since they elongate several hundred-fold their original size. Their growth is determined both by intrinsic and environmental signals. Although nutrients availability in the soil are key factors for a sustained plant growth, the molecular mechanisms underlying their perception and downstream signaling pathways remains unclear. Here, we identified that a low temperature triggers a strong RH cell elongation response involving the cell surface receptor kinase FERONIA (FER) and nutrient sensor TORC1 pathway. We found that FER is required to perceive limited nutrients availability caused by low temperature, to interacts with and activate TORC1-downstream components to trigger RH growth. Nitrates perceived and transported by NRT1.1 were found to mimic this growth response at low temperature. Our findings reveal a new molecular mechanism by which a central hub composed by FER-TORC1 controls RH cell elongation under low temperature.

LRRC15 suppresses SARS-CoV-2 infection and controls collagen production

Although ACE2 is the primary receptor for SARS-CoV-2 infection, a systematic assessment of factors controlling SARS-CoV-2 host interactions has not been described. Here we used whole genome CRISPR activation to identify host factors controlling SARS-CoV-2 Spike binding. The top hit was a Toll-like receptor-related cell surface receptor called leucine-rich repeat-containing protein 15 (LRRC15). LRRC15 expression was sufficient to promote SARS-CoV-2 Spike binding where it forms a cell surface complex with LRRC15 but does not support infection. Instead, LRRC15 functioned as a negative receptor suppressing both pseudotyped and live SARS-CoV-2 infection. LRRC15 is expressed in collagen-producing lung myofibroblasts where it can sequester virus and reduce infection in trans. Mechanistically LRRC15 is regulated by TGF-β, where moderate LRRC15 expression drives collagen production but high levels suppress it, revealing a novel lung fibrosis feedback circuit. Overall, LRRC15 is a master regulator of SARS-CoV-2, suppressing infection and controlling collagen production associated with “long-haul” COVID-19.

The Effects of Pulsed Electric Field On The Interaction Between SARS-Cov-2 And Human ACE2: Y505 Is A Key Target

A novel coronavirus has rapidly spread to almost every country in the world, causing over 233 million confirmed cases of coronavirus disease 2019 (COVID-19) and over 209,761,242 deaths by late September 2021. Binding the receptor binding domain (RBD) to the host cell surface receptor protein, angiotensin converter enzyme (ACE2), is a key step in virus infection. In this study, we applied a pulsed electric field to the RBD/ACE2 complex based on molecular dynamics simulation and demonstrated that the electric field affects the structure and binding affinity of the complex. Additionally, residue Y505 is the crucial medium for the effects of electric field on the complex. Overall, these results may help apply an external electric field to virus suppression.

Integrin/TGF-Beta1 inhibitor GLPG-0187 blocks SARS-CoV-2 Delta and Omicron pseudovirus infection of airway epithelial cells which could attenuate disease severity

As COVID-19 continues to pose major risk for vulnerable populations including the elderly, immunocompromised, patients with cancer, and those with contraindications to vaccination, novel treatment strategies are urgently needed. SARS-CoV-2 infects target cells via RGD-binding integrins either independently or as a co-receptor with surface receptor angiotensin-converting enzyme 2 (ACE2). We used pan-integrin inhibitor GLPG-0187 to demonstrate blockade of SARS-CoV-2 pseudovirus infection of target cells. Omicron pseudovirus infected normal human small airway epithelial (HSAE) cells significantly less than D614G or Delta variant pseudovirus, and GLPG-0187 effectively blocked SARS-CoV-2 pseudovirus infection in a dose-dependent manner across multiple viral variants. GLPG-0187 inhibited Omicron and Delta pseudovirus infection of HSAE cells more significantly than other variants. Pre-treatment of HSAE cells with MEK inhibitor (MEKi) VS-6766 enhanced inhibition of pseudovirus infection by GLPG-0187. Because integrins activate TGF-beta; signaling, we compared plasma levels of active and total TGF-beta; in COVID-19+ patients. Plasma TGF-beta1 levels correlated with age, race, and number of medications upon presentation with COVID-19, but not with sex. Total plasma TGF-beta1 levels correlated with activated TGF-beta1 levels. In our preclinical studies, Omicron infects lower airway lung cells less efficiently than other COVID-19 variants. Moreover, inhibition of integrin signaling prevents SARS-CoV-2 Delta and Omicron pseudovirus infectivity, and may mitigate COVID-19 severity through decreased TGF-beta1 activation. This therapeutic strategy may be further explored through clinical testing in vulnerable and unvaccinated populations.

Synthesis, Physicochemical and Biological Study of Gallium-68- and Lutetium-177-Labeled VEGF-A165/NRP-1 Complex Inhibitors Based on Peptide A7R and Branched Peptidomimetic

Neuropilin-1 (NRP-1) is a surface receptor found on many types of cancer cells. The overexpression of NRP-1 and its interaction with vascular endothelial growth factor-165 (VEGF165) are associated with tumor growth and metastasis. Therefore, compounds that block the VEGF165/NRP-1 interaction represent a promising strategy to image and treat NRP-1-related pathologies. The aim of the presented work was to design and synthesize radioconjugates of two known peptide-type inhibitors of the VEGF165/NRP-1 complex: A7R peptide and its shorter analog, the branched peptidomimetic Lys(hArg)-Dab-Pro-Arg. Both peptide-type inhibitors were coupled to a radionuclide chelator (DOTA) via a linker (Ahx) and so radiolabeled with Ga-68 and Lu-177 radionuclides, for diagnostic and therapeutic uses, respectively. The synthesized radioconjugates were tested for their possible use as theranostic-like radiopharmaceuticals for the imaging and therapy of cancers that overexpress NRP-1. The obtained results indicate good efficiency of the radiolabeling reaction and satisfactory stability, at least 3t1/2 for the 68Ga- and 1t1/2 for the 177Lu-radiocompounds, in solutions mimicking human body fluids. However, enzymatic degradation of both the studied inhibitors caused insufficient stability of the radiocompounds in human serum, indicating that further modifications are needed to sufficiently stabilize the peptidomimetics with inhibitory properties against VEGF165/NRP-1 complex formation.

Directed inter-domain motions enable the IsdH Staphylococcus aureus receptor to rapidly extract heme from human hemoglobin

Pathogenic Staphylococcus aureus actively acquires iron from human hemoglobin (Hb) using the IsdH surface receptor. Heme extraction is mediated by a tridomain unit within the receptor that contains its second (N2) and third (N3) NEAT domains joined by a helical linker domain. Extraction occurs within a dynamic complex, in which receptors engage each globin chain; the N2 domain tightly binds to Hb, while substantial inter-domain motions within the receptor enable its N3 domain to transiently distort the globin's heme pocket. Using molecular simulations, Markov modeling, and quantitative measurements of heme transfer kinetics, we show that directed inter-domain motions within the receptor play a critical role in the extraction process. The directionality of N3 domain motion and the rate of heme extraction is controlled by amino acids within a short, flexible inter-domain tether that connects the N2 and linker domains. In the wild-type receptor directed motions originating from the tether enable the N3 domain to populate configurations capable of distorting Hb's pocket, whereas mutant receptors containing altered tethers are less able to adopt these conformers and capture heme slowly via indirect processes in which Hb first releases heme into the solvent. Thus, our results show inter-domain motions within the IsdH receptor play a critical role in its ability to extract heme from Hb and highlight the importance of directed motions by the short, unstructured, amino acid sequence connecting the domains in controlling the directionality and magnitude of these functionally important motions.

In vivo treatment with M8, a highly diluted tinctures complex, reduced the malignancy of a mouse melanoma model

Background: Cancer is a class of disease responsible for 13% of death cause worldwide. Among all types of cancers, one of the most aggressive and with the highest death rate is melanoma. It is highly metastatic and current treatments with chemotherapeutic drugs do not yield satisfactory results. Therefore, the interest on new therapeutics for cancer treatment has been increasing on research. Highly diluted tinctures (HDT) are intended to enhance immune system responses resulting in reduced frequency of various diseases, and often present no risk of serious side-effects due to its low toxicity. Previous results have demonstrated in vitro inhibition of invasion ability and in vivo anti-metastatic potential of B16F10 lung metastasis model after mice treatment with M8 inhalation. Aims: Now we have evaluated M8 effects on hyaluronic acid and its specific melanoma cell surface receptor (CD44) expression on lungs after inhalation by mice. Methodology: M8 compounds include Aconitum napellus 20dH, Arsenicum album 18dH, Asa foetida 20dH, Calcarea carbonica 16dH, Conium maculatum 17dH, Ipecacuanha 13dH, Phosphorus 20dH, Rhus toxicodendron 17H, Silicea 20dH, Sulphur 24dH, and Thuja occidentalis 19dH. B16F10 Melanoma cells were inoculated into C57B/L6 mouse lateral tail vein. Treatment started 24 hours after inoculation, and was repeated after each 12 hours during 14 days on an inhalation chamber that is adapted to little rodents. Mice were subjected to euthanasia by intraperitoneal injection of thiopental followed by decapitation. Lungs were surgically removed and analyzed under a stereomicroscope for the presence of metastatic foci. They were formaldehyde fixed, dehydrated and paraffin embedded. Histological sections were processed for hematoxilin/eosin (HE), Fontana-Masson and immunohistochemistry staining methods. Images were captured and blindly analysed by ImageJ (NIH) software. Results: HE and Fontana-Masson showed a reduction in number and size of metastatic nodules, as previously demonstrated. We have detected a reduction on hyaluronic acid as well as CD44 expression on mice lungs after M8 treatment. The high metastatic potential of melanoma is proportional to hyaluronic acid expression level, together with its specific cell surface receptor, the CD44. These results suggest that M8 treatment reduces malignancy of mouse melanoma through modulation of hyaluronic acid and CD44 expression, which play crucial roles in tumor invasion and growth. Conclusion: Even though further investigation are necessary to elucidate the mechanisms of action of M8 treatment there is an indication that these highly diluted tinctures could be a promising therapy to treat metastatic melanoma.