Intrinsic disorder perspective of an interplay between the renin-angiotensin-aldosterone system and SARS-CoV-2

Abstract

The novel severe acute respiratory syndrome (SARS) coronavirus SARS-CoV-2 walks the planet causing the rapid spread of the CoV disease 2019 (COVID-19) that has especially deleterious consequences for the patients with underlying cardiovascular diseases (CVDs). Entry of the SARS-CoV-2 into the host cell involves interaction of the virus (via the receptor-binding domain (RBD) of its spike glycoprotein) with the membrane-bound form of angiotensin-converting enzyme 2 (ACE2) followed by the virus-ACE2 complex internalization by the cell. Since ACE2 is expressed in various tissues, such as brain, gut, heart, kidney, and lung, and since these organs represent obvious targets for the SARS-CoV-2 infection, therapeutic approaches were developed to either inhibit ACE2 or reduce its expression as a means of prevention of the virus entry into the corresponding host cells. The problem here is that in addition to be a receptor for the SARS-CoV-2 entry into the host cells, ACE2 acts as a key component of the renin-angiotensin-aldosterone system (RAAS) aimed at the generation of a cascade of vasoactive peptides coordinating several physiological processes. In RAAS, ACE2 degrades angiotensin II, which is a multifunctional CVD-promoting peptide hormone and converts it to a heptapeptide angiotensin-(1-7) acting as the angiotensin II antagonist. As protein multifunctionality is commonly associated with the presence of flexible or disordered regions, we analyze here the intrinsic disorder predisposition of major players related to the SARS-CoV-2 - RAAS axis. We show that all considered proteins contain intrinsically disordered regions that might have specific functions. Since intrinsic disorder might play a role in the functionality of query proteins and be related to the COVID-19 pathogenesis, this work represents an important disorder-based outlook of an interplay between the renin-angiotensin-aldosterone system and SARS-CoV-2. It also suggests that consideration of the intrinsic disorder phenomenon should be added to the modern arsenal of means for drug development.

Fig. 1

Structure and intrinsic disorder propensity of spike glycoprotein from SARS-CoV-2. A. A 3.46 Å resolution cryo-EM structure of a homotrimeric form of spike glycoprotein from SARS-CoV-2 (PDB ID: 6VSB). B. A X-ray crystal structure (resolution of 2.45 Å) of a complex between the human ACE2 receptor (blue structure) and the RBD of the S protein from SARS-CoV-2 (red structure) (PDB ID: 6M0J). C. Intrinsic disorder profile generated for the S protein from SARS-CoV-2 by DiSpi web-crawler aggregate the results from a set of commonly used predictors of intrinsic disorder, such as PONDR® VLXT (Romero et al., 2001), PONDR® VL3 (Peng et al., 2006), PONDR® VLS2B (Peng et al., 2005), PONDR® FIT (Xue et al., 2010), IUPred2 (Short) and IUPred2 (Long) (Dosztanyi et al., 2005a, Dosztanyi et al., 2005b). This tool enables the rapid generation of disorder profile plots for individual polypeptides as well as arrays of polypeptides.

Fig. 2

Structural characterization of the renin-angiotensin-aldosterone system members. A. High resolution (1.8 Å) X-ray crystal structure of human renin (PDB ID: 1HRN) (Tong et al., 1995). B. X-ray crystal structure of human angiotensinogen (PDB ID: 2WXW) (Zhou et al., 2010). C. Overlaid crystal structures of the peptidase M2 1 domain (N-domain, residues 30–658; PDB ID: 3NXQ:A (Anthony et al., 2010)) and the peptidase M2 2 domain (C-domain, residues 642–1232; PDB ID: 2IUL; (Watermeyer et al., 2006)) shown by red and blue colors, respectively. Multiple structure alignment was conducted using the MultiProt algorithm (Shatsky et al., 2004), and VMD platform was used to generate this image (Humphrey et al., 1996). D. Crystal structure of angiotensin II type 1 receptor (AT₁R, blue chain) bound to the angiotensin-like peptideS1I8 (red chain) and stabilized by the nanobody (cyan and yellow chains) (PDB ID: (Wingler et al., 2019)). E, crystal structure of the chimera protein of human AT1R and soluble cytochrome b₅₆₂ from Escherichia coli (PDB ID: 5UNG; (Zhang et al., 2017)).

Fig. 3

Disorder profiles generated for the members of human RAAS by the D²P² computational platform (plots A, B, C, D, E, F, and G) and by the DiSpi web-crawler (plots a, b, c, d, e, f, and g). A, a. Prorenin (UniProt ID: P00797); B, b. Angiotensinogen (UniProt ID: P01019); C, c. Angiotensin-converting enzyme 1 (UniProt ID: P12821); D, d. Angiotensin-converting enzyme 2 (UniProt ID: Q9BYF1); E, e. Type-1 angiotensin II receptor (UniProt ID: P30556); F, f. Type-2 angiotensin II receptor (UniProt ID: P50052); G, g. Proto-oncogene Mas (MAS1; UniProt ID: P04201).

Fig. 4

NMR solution structure of the angiotensin I (PDB ID: 1N9U; (Spyroulias et al., 2003)).

Fig. 5

Analysis of the internal (A) and external (B) interactability of the RAAS members conducted by Search Tool for the Retrieval of Interacting Genes (STRING, http://string-db.org/) that generates a network of predicted associations based on predicted and experimentally-validated information on the interaction partners of a protein of interest (Szklarczyk et al., 2011). In the corresponding network, the nodes correspond to proteins, whereas the edges show predicted or known functional associations. Seven types of evidence are used to build the corresponding network, where they are indicated by the differently colored lines: a green line represents neighborhood evidence; a red line - the presence of fusion evidence; a purple line - experimental evidence; a blue line – co-occurrence evidence; a light blue line - database evidence; a yellow line – text mining evidence; and a black line – co-expression evidence (Szklarczyk et al., 2011).

Fig. 6

Intrinsic disorder and interactability of human transmembrane protease TMPRSS2 (UniProt ID: O15393). A. Disorder profile generated by the DiSpi web-crawler. B. Functional disorder profile generated by the D²P² computational platform. C. TMPRSS2-centered PPI network generated by STRING (http://string-db.org/).