BREAKING! U.S. NIH Study Finds That SARS-CoV-2 Spike Proteins And mRNAs Can Translocate Into The Nucleus Of Host Cells Unlike Any Other Coronaviruses!
A new study involving researchers from the U.S.NIH, US. NIAID, University of North Dakota School of Medicine & Health and University of Nebraska Medical Center have alarmingly found that unlike any other known coronaviruses, the SARS-CoV-2 spike proteins and S mRNAs are able to translocate into the nucleus of human host cells and contribute to pathogenesis.
The study findings have numerous implications including the usage of spike proteins is in various therapeutic and prophylactic products, the treatment protocols of COVID-19 and also the various contributing factors and symptoms of Long COVID!
The SARS-CoV-2 virus causes severe pathophysiology in vulnerable older populations and appears to be highly pathogenic and more transmissible than SARS-CoV or MERS-CoV.
The spike (S) protein appears to be a major pathogenic factor that contributes to the unique pathogenesis of SARS-CoV-2. Although the S protein is a surface transmembrane type 1 glycoprotein, it has been predicted to be translocated into the nucleus due to the novel nuclear localization signal (NLS) “PRRARSV”, which is absent from the S protein of other coronaviruses.
The study findings found that besides S proteins being able to translocate into the nucleus in SARS-CoV-2-infected human host cells, surprisingly, the S mRNAs also translocated into the nucleus.
It was found that S mRNA colocalizes with S protein, aiding the nuclear translocation of S mRNA.
Although the nuclear translocation of nucleoprotein (N) has been shown in many coronaviruses, the nuclear translocation of both S mRNA and S protein reveals a novel and unique pathogenic feature of SARS-CoV-2.
Corresponding author, Dr Masfique Mehedi from the Department of Biomedical Sciences, University of North Dakota School of Medicine & Health told Thailand Medical News
, “It is now found that one of the novel sequence insertions resides at the S1/S2 boundary of Spike (S) protein and constitutes a functional nuclear localization signal (NLS) motif “PRRARSV”, which may supersede the importance of previously proposed polybasic furin cleavage site “RRAR”. Indeed, S protein’s NLS-driven nuclear translocation and its possible role in S mRNA’s nuclear translocation reveal a novel pathogenic feature of SARS-CoV-2.”
The study findings were published on a preprint server and are currently being peer reviewed.
The study findings are a major breakthrough after 34 months since the COVID-19 pandemic first started and has killed more than 6.55 million people globally according to reported figures. (Actual figures are expected to be about 5 to 6-fold not including excess deaths!)
With an estimate that almost 3 billion of the world population already exposed to the SARS-CoV-2 virus with many not even being aware, the burden form Long COVID is expected to literally expected to crash the global public healthcare infrastructure in coming months and years!
The study findings are the first to validate that the
SARS-COV-2 spike (S) protein and S messenger ribonucleic acid (mRNA) nuclear co-translocation as a novel feature of SARS-CoV-2 pathogenesis.
The SARS-CoV-2 S protein has been documented as a key factor for SARS-CoV-2 pathogenicity due to its broad tropism for the human angiotensin-converting enzyme 2 (hACE2) receptor.
Numerous past studies have investigated SARS-CoV-2 protein subcellular localization in vitro; however, comprehensive data on the S glycoprotein needs are limited and require further investigation.
The study team explored S and S mRNA nuclear translocation as underlying mechanisms of SARS-CoV-2 pathogenicity.
For the study, primary normal human bronchial epithelial (NHBE) cells were obtained from healthy non-smoker individuals and chronic obstructive pulmonary disease (COPD) patients to form a pseudostratified bronchial airway epithelium.
These airway cells were infected with the SARS-CoV-2 USA/WA-CDC-WA1/2020 strain, SARS-CoV Urbani strain, and MERS-CoV for in vitro experiments.
The study team investigated whether SARS-CoV-2 S translocated into the SARS-CoV-2-infected airway epithelial cell nucleus and colocalized with S mRNA.
In the study, the cells were subjected to immunohistochemistry (IHC) analysis and were examined by confocal microscopy (CFM).
Subsequently, immunofluorescence analysis was performed for SARS-CoV-2 protein and S mRNA detection.
The S sequences of both the viruses were aligned by the multiple sequence alignment (MSA) technique to determine whether the SARS-CoV-2 isolate has multiple novel sequence insertions (SIs) in S compared to the Urbani strain of SARS-CoV.
Further, SARS-CoV-2 Spike proteins were analyzed utilizing in silico analysis to investigate whether S resembled or constituted protein motifs such as a nuclear localization signal (NLS) and to study the interactions between SARS-CoV-2 RNA and the S and nucleocapsid (N) proteins.
Nuclear localization signal or NLS estimation was performed for several pathogenic CoV S proteins.
The study team also investigated whether the “RRAR” polybasic site could be an NLS motif and whether the NLS motif was functional concerning the polybasic RRAR site at the boundary between S subunits 1 (S1) and 2 (S2).
The study findings showed that only SARS-CoV-2 S contained a functional NLS motif “PRRARSV” of pat7-type at the S1/S2 boundary due to the presence of the novel ‘NSPR’ SI and drove nuclear translocation of S protein (and S mRNA) in the airway epithelial cells infected by SARS-CoV-2.
Importantly, SARS-CoV-2 S mRNA was found to be nuclear (<10%) and abundant (~90%) in the cytoplasm, indicative of mRNA transition. In less than one percent of cases, complete translocation of S protein mRNA was observed.
Both, intracellular S and S protein mRNA distribution was observed, indicative of nuclear translocation, involving the outer surface and the inside of the nucleus.
The S and S protein mRNA colocalized and formed a protein-mRNA complex in the infected cells, 85% of which was detected outside the nucleus.
Also, the N proteins of MERS-CoV, SARS-CoV, and SARS-CoV-2 demonstrated nuclear translocation.
Spike proteins translocated into the nucleus (25%) of the airway cells through the cytoplasmic endoplasmic reticulum (ER)-Golgi apparatus pathway, and 15% of the S protein was detected at the nuclear surface, indicative of a transitionary stage in protein translocation.
It was noted that the nuclear translocation of S mRNA located on the nucleus's surface was associated with and assisted by SARS-CoV-2 S.
However, in contrast, S mRNA present in the cytoplasmic did not show such associations. NLS-facilitated translocations into the nucleus were observed for MERS-CoV, SARS-CoV, and SARS-CoV-2.
The study findings showed that nuclear translocation and co-localization of the S glycoprotein and S mRNA are novel mechanisms of SARS-CoV-2 pathogenesis.
Also, the S glycoprotein mRNA nuclear translocation was facilitated by the S protein due to the presence of the functional pat7 NLS “PRRARSV” motif in SARS-CoV-2 S.
These study findings could aid the development of effective S-targeted agents to widen the therapeutic landscape of COVID-19.
Importantly, the novel SARS-CoV-2 nuclear translocation indicates that S protein surface expression may be reduced, but its impact on host immune recognition needs to be determined. S and S mRNA colocalization indicate that the SARS-CoV-2 S may contain an RNA-binding motif and therefore, must be investigated further.
The study findings have numerous implications as well about the usage of these SARS-CoV-2 spike proteins in certain prophylactic and therapeutic applications. Further urgent studies are warranted about the usage of the spike proteins in the current COVID therapeutics and their effects on the human race!
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