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Hoter, A., and H. Y. Naim, "Biochemical Characterization of SARS-CoV-2 Spike RBD Mutations and Their Impact on ACE2 Receptor Binding.", Frontiers in molecular biosciences, vol. 9, pp. 893843, 2022. Abstract

Infection of mammalian cells by SARS-CoV-2 coronavirus requires primary interaction between the receptor binding domain (RBD) of the viral spike protein and the host cell surface receptor angiotensin-converting enzyme 2 (ACE2) glycoprotein. Several mutations in the RBD of SARS-CoV-2 spike protein have been reported for several variants and resulted in wide spread of the COVID pandemic. For instance, the double mutations L452R and E484Q present in the Indian B.1.617 variant have been suggested to cause evasion of the host immune response. The common RBD mutations N501Y and E484K were found to enhance the interaction with the ACE2 receptor. In the current study, we analyzed the biosynthesis and secretion of the RBD double mutants L452R and E484Q in comparison to the wild-type RBD and the individual mutations N501 and E484K in mammalian cells. Moreover, we evaluated the interaction of these variants with ACE2 by means of expression of the S protein and co-immunoprecipitation with ACE2. Our results revealed that the double RBD mutations L452R and E484Q resulted in a higher expression level and secretion of spike S1 protein than other mutations. In addition, an increased interaction of these mutant forms with ACE2 in Calu3 cells was observed. Altogether, our findings highlight the impact of continuous S1 mutations on the pathogenicity of SARS-CoV-2 and provide further biochemical evidence for the dominance and high transmissibility of the double Indian mutations.

Hoter, A., "Combined Thermotherapy and Heat Shock Protein Modulation for Tumor Treatment Abdullah", Heat Shock Proteins in Human Diseases, Switzerland AG 2021, Springer Cham, 2021.
Hoter, A., S. Rizk, and H. Y. Naim, "Heat Shock Protein 60 in Hepatocellular Carcinoma: Insights and Perspectives.", Frontiers in molecular biosciences, vol. 7, pp. 60, 2020. Abstract

Heat shock protein 60 (HSP60) is a mitochondrial chaperone that is implicated in physiological and pathological processes. For instance, it contributes to protein folding and stability, translocation of mitochondrial proteins, and apoptosis. Variations in the expression levels of HSP60 have been correlated to various diseases and cancers, including hepatocellular carcinoma (HCC). Unlike other HSPs which clearly increase in some cancers, data about HSP60 levels in HCC are controversial and difficult to interpret. In the current review, we summarize and simplify the current knowledge about the role of HSP60 in HCC. In addition, we highlight the possibility of its targeting, using chemical compounds and/or genetic tools for treatment of HCC.

Hoter, A., S. Rizk, and H. Y. Naim, "Cellular and Molecular Adaptation of Arabian Camel to Heat Stress.", Frontiers in genetics, vol. 10, pp. 588, 2019. Abstract

To cope with the extreme heat stress and drought of the desert, the Arabian camel () has developed exceptional physiological and biochemical particularities. Previous reports focused mainly on the physiological features of Arabian camel and neglected its cellular and molecular characteristics. Heat shock proteins are suggested to play a key role in the protein homeostasis and thermotolerance. Therefore, we aim by this review to elucidate the implication of camel HSPs in its physiological adaptation to heat stress and compare them with HSPs in related mammalian species. Correlation of these molecules to the adaptive mechanisms in camel is of special importance to expand our understanding of the overall camel physiology and homeostasis.

Hoter, A., and H. Y. Naim, "The Functions and Therapeutic Potential of Heat Shock Proteins in Inflammatory Bowel Disease-An Update.", International journal of molecular sciences, vol. 20, issue 21, 2019. Abstract

Inflammatory bowel disease (IBD) is a multifactorial human intestinal disease that arises from numerous, yet incompletely defined, factors. Two main forms, Crohn's disease (CD) and ulcerative colitis (UC), lead to a chronic pathological form. Heat shock proteins (HSPs) are stress-responsive molecules involved in various pathophysiological processes. Several lines of evidence link the expression of HSPs to the development and prognosis of IBD. HSP90, HSP70 and HSP60 have been reported to contribute to IBD in different aspects. Moreover, induction and/or targeted inhibition of specific HSPs have been suggested to ameliorate the disease consequences. In the present review, we shed the light on the role of HSPs in IBD and their targeting to prevent further disease progression.

Hoter, A., and H. Y. Naim, "Heat Shock Proteins and Ovarian Cancer: Important Roles and Therapeutic Opportunities.", Cancers, vol. 11, issue 9, 2019. Abstract

Ovarian cancer is a serious cause of death in gynecological oncology. Delayed diagnosis and poor survival rates associated with late stages of the disease are major obstacles against treatment efforts. Heat shock proteins (HSPs) are stress responsive molecules known to be crucial in many cancer types including ovarian cancer. Clusterin (CLU), a unique chaperone protein with analogous oncogenic criteria to HSPs, has also been proven to confer resistance to anti-cancer drugs. Indeed, these chaperone molecules have been implicated in diagnosis, prognosis, metastasis and aggressiveness of various cancers. However, relative to other cancers, there is limited body of knowledge about the molecular roles of these chaperones in ovarian cancer. In the current review, we shed light on the diverse roles of HSPs as well as related chaperone proteins like CLU in the pathogenesis of ovarian cancer and elucidate their potential as effective drug targets.

Hoter, A., S. Rizk, and H. Y. Naim, "The Multiple Roles and Therapeutic Potential of Molecular Chaperones in Prostate Cancer.", Cancers, vol. 11, issue 8, 2019. Abstract

Prostate cancer (PCa) is one of the most common cancer types in men worldwide. Heat shock proteins (HSPs) are molecular chaperones that are widely implicated in the pathogenesis, diagnosis, prognosis, and treatment of many cancers. The role of HSPs in PCa is complex and their expression has been linked to the progression and aggressiveness of the tumor. Prominent chaperones, including HSP90 and HSP70, are involved in the folding and trafficking of critical cancer-related proteins. Other members of HSPs, including HSP27 and HSP60, have been considered as promising biomarkers, similar to prostate-specific membrane antigen (PSMA), for PCa screening in order to evaluate and monitor the progression or recurrence of the disease. Moreover, expression level of chaperones like clusterin has been shown to correlate directly with the prostate tumor grade. Hence, targeting HSPs in PCa has been suggested as a promising strategy for cancer therapy. In the current review, we discuss the functions as well as the role of HSPs in PCa progression and further evaluate the approach of inhibiting HSPs as a cancer treatment strategy.

Hoter, A., M. Amiri, M. Warda, and H. Y. Naim, "Molecular cloning, cellular expression and characterization of Arabian camel (Camelus dromedarius) endoplasmin.", International journal of biological macromolecules, vol. 117, pp. 574-585, 2018 Oct 01. Abstract

Endoplasmin, or GRP94, is an ER-located stress inducible molecular chaperone implicated in the folding and assembly of many proteins. The Arabian one-humped camel lives in an environment of thermal stress, nevertheless is able to encounter the risk of misfolded proteins. Here, the cDNA encoding camel GRP94 was isolated by rapid amplification of cDNA ends. The isolated cDNA contained an open reading frame of 2412 bp encoding a protein of 803 amino acids with predicted molecular mass of 92.5 kDa. Nucleotide and protein BLAST analysis of cGRP94 revealed strong conservation between camel and other domestic mammals. Overexpression of cGRP94 in COS-1 cells revealed multiple isoforms including one N-glycosylated species. Immunofluorescence colocalized cGRP94 with the ER resident protein calnexin. Interestingly, none of the cGRP94 isoforms expressed in CHO cells was N-glycosylated, presumably due to folding determinants that mask the N-glycosylation sites as proposed by in silico modelling. Surprisingly, isoforms of cGRP94 were detected in the culture media of transfected cells indicating that the protein, although an ER resident, also is trafficked and secreted into the exterior milieu. The overall striking structural homologies of GRP94s among mammalian reflect their pivotal role in the ER quality control and protein homeostasis.

Hoter, A., M. Amiri, A. Prince, H. Amer, M. Warda, and H. Y. Naim, "Differential Glycosylation and Modulation of Camel and Human HSP Isoforms in Response to Thermal and Hypoxic Stresses.", International journal of molecular sciences, vol. 19, issue 2, 2018 Jan 30. Abstract

Increased expression of heat shock proteins (HSPs) following heat stress or other stress conditions is a common physiological response in almost all living organisms. Modification of cytosolic proteins including HSPs by -GlcNAc has been shown to enhance their capabilities for counteracting lethal levels of cellular stress. Since HSPs are key players in stress resistance and protein homeostasis, we aimed to analyze their forms at the cellular and molecular level using camel and human HSPs as models for efficient and moderate thermotolerant mammals, respectively. In this study, we cloned the cDNA encoding two inducible HSP members, HSPA6 and CRYAB from both camel () and human in a Myc-tagged mammalian expression vector. Expression of these chaperones in COS-1 cells revealed protein bands of approximately 25-kDa for both camel and human CRYAB and 70-kDa for camel HSPA6 and its human homologue. While localization and trafficking of the camel and human HSPs revealed similar cytosolic localization, we could demonstrate altered glycan structure between camel and human HSPA6. Interestingly, the glycoform of camel HSPA6 was rapidly formed and stabilized under normal and stress culture conditions whereas human HSPA6 reacted differently under similar thermal and hypoxic stress conditions. Our data suggest that efficient glycosylation of camel HSPA6 is among the mechanisms that provide camelids with a superior capability for alleviating stressful environmental circumstances.

Hoter, A., M. E. El-Sabban, and H. Y. Naim, "The HSP90 Family: Structure, Regulation, Function, and Implications in Health and Disease.", International journal of molecular sciences, vol. 19, issue 9, 2018 Aug 29. Abstract

The mammalian HSP90 family of proteins is a cluster of highly conserved molecules that are involved in myriad cellular processes. Their distribution in various cellular compartments underlines their essential roles in cellular homeostasis. HSP90 and its co-chaperones orchestrate crucial physiological processes such as cell survival, cell cycle control, hormone signaling, and apoptosis. Conversely, HSP90, and its secreted forms, contribute to the development and progress of serious pathologies, including cancer and neurodegenerative diseases. Therefore, targeting HSP90 is an attractive strategy for the treatment of neoplasms and other diseases. This manuscript will review the general structure, regulation and function of HSP90 family and their potential role in pathophysiology.