In a overview article revealed within the journal Sign Transduction and Focused Remedy, scientists have mentioned host metabolic alteration triggered by extreme acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and its impact on illness severity.
Examine: Metabolic alterations upon SARS-CoV-2 an infection and potential therapeutic targets in opposition to coronavirus an infection. Picture Credit score: NIAID
Background
Extreme acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative pathogen of coronavirus illness 2019 (COVID-19) pandemic, is an enveloped positive-sense, single-stranded RNA virus belonging to the human beta-coronavirus household. The virus enters host cells by interacting with the host cell membrane receptor angiotensin-converting enzyme 2 (ACE2) by its floor glycoprotein, the spike protein.
Host metabolism performs important a job in regulating varied physiological processes throughout viral replication. Conversely, many viruses can modulate host metabolism to assist their lifecycle inside host cells and evade host immune responses.
Research have proven that viruses can alter host lipid metabolism to create replication compartments. In COVID-19 sufferers, an accumulation of lipids has been noticed within the lungs. Lipid sample alterations induced by SARS-CoV-2 have been discovered to affiliate with illness severity.
Kind 2 diabetes has been recognized as one of many important danger elements for extreme COVID-19 and mortality. Elevated glycolysis has been noticed in all immune cells in COVID-19 sufferers. These observations spotlight an affiliation between SARS-CoV-2 an infection and glucose metabolic alteration.
SARS-CoV-2 host cell entry
The interplay between spike protein and ACE2 by the spike S1 area results in the cleavage of spike protein by host transmembrane protease TMPRSS2 on the S2 website. That is adopted by the fusion of the viral envelope and host lipid bilayer and the discharge of viral particles into host cells.
Lipid rafts are microdomains containing lipid molecules, together with cholesterols and sphingolipids. Proof exhibits that lipid rafts situated on the host cell membrane play essential roles within the SARS-CoV-2 entry course of by offering platforms for membrane receptors. Lipid rafts also can assist cell-to-cell viral transmission by facilitating syncytia formation. Lipid raft disruption induced by ldl cholesterol trafficking from the membrane to the endoplasmic reticulum (ER) has been discovered to scale back SARS-CoV-2 host cell entry.
SARS-CoV-2 spike protein can immediately bind to ldl cholesterol and receptor-bound high-density lipoprotein (HDL). The spike protein has been discovered to seize lipid elements from cell membranes by bindings to and altering the operate of HDL.
As with membrane ldl cholesterol, intracellular ldl cholesterol can also be concerned in viral entry. Genetical screening by CRISPR libraries have recognized sure genes associated to ldl cholesterol metabolism which can be important for SARS-CoV-2 an infection.
Varied sphingolipids, particularly ceramide, and sphingosine, play outstanding roles in SARS-CoV-2 host cell entry. Ceramide is transformed from sphingomyelin by acid sphingomyelinase (ASM) or synthesized de novo from palmitoyl CoA and serine. Ceramide has been discovered to facilitate SARS-CoV-2 entry by forming ceramide-rich microdomains the place ACE2 clusters. A number of ASM inhibitors have been discovered to forestall SARS-CoV-2 entry by altering floor ceremide ranges.
Sphingosine is derived from ceramide by ceramidase catalyzation or sphingosine 1-phosphate (S1P) by S1P phosphatase catalyzation. In distinction to ceremide, sphingosine has been discovered to forestall viral entry by binding to ACE2 and blocking the spike-ACE2 interplay. S1P, a downstream product of sphingosine, has additionally been discovered to enhance COVID-19 medical presentation by defending the endothelial barrier.
Modification of SARS-CoV-2 spike protein
Proof exhibits that the SARS-CoV-2 entry course of could be regulated by lipid-mediated post-translational modification of the spike protein. The binding of linoleic acid to the spike protein has been discovered to lock the protein in a closed conformation, resulting in the inhibition of viral entry.
In distinction, covalent attachment of fatty acids to the spike protein (palmitoylation) has been discovered to advertise viral entry by stabilizing the spike protein homotrimer. Spike protein palmitoylation is a conserved course of throughout all coronaviruses.
In sort 2 diabetes, excessive blood glucose degree has been discovered to advertise viral entry by rising ACE2 expression. As well as, spike protein glycosylation (covalent attachment of sugar moieties) has been discovered to modulate the viral entry course of considerably.
SARS-CoV-2 replication
In addition to viral entry, host lipids modulate SARS-CoV-2 replication. Research have proven that glycerophospholipid metabolism promotes viral replication by triggering the formation of double-membrane vesicles.
Current proof has proven that SARS-CoV-2 makes use of host lipid droplets to fulfill the power demand of replication. TMEM41B, an ER-localized protein answerable for lipid mobilization from lipid droplets, has been recognized as an important host issue for SARS-CoV-2 replication.
Like many different viruses, SARS-CoV-2 induces the “Warburg impact” (a shift of glucose metabolism to cardio glycolysis) to facilitate replication. Glycolysis supplies power and constructing blocks for nucleotide synthesis, that are conditions for viral replication.
One carbon metabolism additionally facilitates SARS-CoV-2 replication by offering supplies for RNA capping, which is required for stopping RNA degradation by innate immune responses and facilitating viral protein translation.
SARS-CoV-2 meeting
Host lipids play essential roles in SARS-CoV-2 meeting. Research have proven that viral membrane protein makes use of a number of lipid elements to induce membrane curvature. Equally, palmitoylation has been discovered to assist viral meeting by stabilizing envelop protein and sustaining its purposeful structure.
Drug repurposing
Contemplating the numerous involvement of host metabolism in SARS-CoV-2 an infection, a number of lipid-modulating and glucose-modulating medicine, together with statins, ASM inhibitors, non-steroidal anti-inflammatory medicine, montelukast, omega-3 fatty acids, 2-deoxy-D-glucose, and metformin, have been repurposed to handle COVID-19. These medicine are presently beneath medical investigation for treating COVID-19 sufferers.
