N-degron-mediated degradation of the proteolytically activated form of PKC-theta kinase attenuates its pro-apoptotic function.

Cellular signalling cues lead to the initiation of apoptotic pathways and often result in the activation of caspases which in turn cause the generation of proteolytically generated protein fragments with new or altered functions. Mounting number of studies reveal that the activity of these proteolytically activated protein fragments can be counteracted via their selective degradation by the N-degron degradation pathways. Here, we investigate the proteolytically generated fragment of the PKC theta kinase, where we demonstrate the first report on the stability of this pro-apoptotic protein fragment. We have determined that the pro-apoptotic cleaved fragment of PKC-theta is unstable in cells because its N-terminal lysine targets it for proteasomal degradation via the N-degron degradation pathway and this degradation is inhibited by mutating the destabilizing N-termini, knockdown of the UBR1 and UBR2 E3 ligases. Tellingly, we demonstrate that the metabolic stabilization of the cleaved fragment of PKC-theta or inhibition of the N-degron degradation augments the apoptosis-inducing effect of staurosporine in Jurkat cells. Notably, we have unveiled that the cleaved fragment of PKC theta, per se, can induce apoptotic cell death in Jurkat T-cell leukemia. Our results expand the functional scope of mammalian N-degron degradation pathways, and support the notion that targeting N-degron degradation machinery may have promising therapeutic implications in cancer cells.

Interference of Chaga mushroom terpenoids with the attachment of SARS-CoV-2; in silico perspective.

Finding a potent inhibitor to the pandemic SARS-CoV-2 is indispensable nowadays. Currently, in-silico methods work as expeditious investigators to screen drugs for possible repurposing or design new ones. Targeting one of the possible SARS-CoV-2 attachment and entry receptors, Glucose-regulated protein 78 (GRP78), is an approach of major interest. Recently, GRP78 was reported as a recognized representative in recognition of the latest variants of SARS-CoV-2. In this work, molecular docking and molecular dynamics simulations were performed on the host cell receptor GRP78. With its many terpenoid compounds, Chaga mushroom was tested as a potential therapeutic against the SARS-CoV-2 receptor, GRP78. Results revealed low binding energies (high affinities) toward the GRP78 substrate-binding domain ß (SBDß) of Chaga mushroom terpenoids. Even the highly specific cyclic peptide Pep42, which selectively targeted GRP78 over cancer cells in vivo, showed lower binding affinity against GRP78 SBDß compared to the binding affinities of terpenoids. These are auspicious results that need to be tested experimentally. Intriguingly, terpenoids work as a double sword as they can be used to interfere with VUI 202,012/01, 501.V2, and B.1.1.248 variants of SARS-CoV-2 spike recognition.

GRP78: A possible relationship of COVID-19 and the mucormycosis; in silico perspective.

Mucormycosis is a severe fungal infection reported in many cancer survivors, diabetic and immune-suppressed patients during organ transplants. A vast spark in the reported COVID-19 cases is noticed in India during the second wave in May 2021, when Mucormycosis is declared an epidemic. Despite being a rare disease, the mortality rate associated with Mucormycosis is more than 40%. Spore coat proteins (CotH) are essential proteins in many pathogenic bacteria and fungi. CotH3 was reported as the vital protein required for fungal virulence in Mucormycosis. We previously reported the involvement of the host cell-surface receptor GRP78 in SARS-CoV-2 spike recognition. Additionally, GRP78 is known to be the virulence factor during Mucormycosis. Using state-of-the-art structural bioinformatics and molecular modeling tools, we predicted the GRP78 binding site to the Rhizopus delemar CotH3 protein. Our findings pave the way toward rationally designing small molecule inhibitors targeting the GRP78 and its counter proteins in both pathogenic viral (SARS-CoV-2 spike) and fungal (R. delemar CotH3) diseases.