New insights into the putative role of leucine-rich repeat proteins of Leptospira interrogans and their participation in host cell invasion: an in silico analysis

Abstract

Pathogenic Leptospira are spirochetes that cause leptospirosis, a worldwide zoonotic disease. Leptospirosis affects humans and animals, with approximately 1 million human infections and 60,000 deaths per year. The diversity of leptospiral strains and serovars allied to the fact that pathogenesis is not yet fully understood, make the development of an effective vaccine against leptospirosis a challenge. Outer membrane and secreted proteins are considered potential antigens since they play a vital role in mediating interactions with host molecules. Several domains or motifs have been reported to participate in the leptospiral infection process. Among them, leucine-rich repeat (LRR) proteins have been highlighted as attractive multipurpose proteins, exhibiting a broad spectrum of ligands and having a putative role in bacterial pathogenesis. Indeed, genome annotation of leptospiral species pointed out that LRR proteins are predominant in pathogenic strains, a feature that corroborates this hypothesis. A few LRR proteins of L. santarosai, L. borgpetersenii and L. interrogans have been studied and their possible role in virulence was proposed. Yet, a mechanistic and broad investigation of LRR proteins was not fully performed. In this review, a comprehensive in silico analysis of 21 LRR proteins of L. interrogans was performed in relation to structure, function, dynamics and virulent potential that will contribute to understanding the key role of these domains in the underlying mechanisms of leptospiral infection.

Keywords: LRR proteins; Leptospira; in sílico analysis; leptospirosis; pathogenesis.

Figure 1

LRR amino acids sequence conservation analysis among the different Leptospira spp. Heatmap showing the conservation level among pathogenic (P1+ and P1-), intermediate (P2) and saprophytic (S1 and S2) species of Leptospira. Heatmap was elaborated based in the c value among the orthologs of LRR proteins.

Figure 2

Representative scheme and distribution of LRR domains. Schematic representation of LRR proteins from L. interrogans according to SMART webserver (http://smart.embl-heidelberg.de). Each sequence shown in yellow represents a LRR domain; WGR and DUF domains are also demonstrated. Scale is representative of the amino acids sequence.

Figure 3

Tertiary structure prediction of L. interrogans LRR proteins and spatial alignment with LIC_10831. Amino acid sequences of proteins LIC_10828, LIC_10829, LIC_10830, LIC_11051, LIC_11097, LIC_11098, LIC_11180, LIC_11504, LIC_11507, LIC_11505, LIC_12234, LIC_12375, LIC_12401, LIC_12512, LIC_12676, LIC_12759, LIC_12899, LIC_12901, LIC_20055, LIC_20154 were submitted to the AlphaFold2 program, and the best score was selected. Superposition of LIC_10831 (green) with the other LRR proteins (red) was performed by PyMOL softaware. (*) refers to the presence of WGR domain.

Figure 4

Tertiary structure prediction of L. interrogans LRR proteins and spatial alignment with InlB of L. monocytogenes. Amino acid sequences of proteins LIC_10828, LIC_10829, LIC_10830, LIC_10831, LIC_11051, LIC_11097, LIC_11098, LIC_11180, LIC_11504, LIC_11507, LIC_11505, LIC_12234, LIC_12375, LIC_12401, LIC_12512, LIC_12676, LIC_12759, LIC_12899, LIC_12901, LIC_20055, LIC_20154. Superposition of InlB (green) with the other LRR proteins (red) was performed by PyMOL softaware. (*) refers to the presence of WGR domain.

Figure 5

Gene ontology (GO) enrichment analysis of L. interrogans LRR proteins. The search was performed using Argot2.5 tool and a threshold of 200 was considered to determine hits for molecular function (A), cellular component (B) and biological process (C) among the LRR proteins.