Abstract
Lipid rafts are dynamic, nanoscale assemblies of specific proteins and lipids, distributed heterogeneously on eukaryotic membrane. Flotillin-1, a conserved eukaryotic raft marker protein (RMP) harbor SPFH (Stomatin, Prohibitin, Flotillin, and HflK/C) and oligomerization domains to regulate various cellular processes through its interactions with other signaling or transport proteins. Rafts were thought to be absent in prokaryotes hitherto, but recent report of its presence and significance in physiology of Bacillus subtilis prompted us to investigate the same in pathogenic bacteria (PB) also. In prokaryotes, proteins of SPFH2a subfamily show highest identity to SPFH domain of Flotillin-1. Moreover, bacterial genome organization revealed that Flotillin homolog harboring SPFH2a domain exists in an operon with an upstream gene containing NFeD domain. Here, presence of RMP in PB was initially investigated in silico by analyzing the presence of SPFH2a, oligomerization domains in the concerned gene and NfeD domain in the adjacent upstream gene. After investigating 300 PB, four were found to harbor RMP. Among them, domains of Bas0525 (FlotP) of Bacillus anthracis (BA) showed highest identity with characteristic domains of RMP. Considering the global threat of BA as the bioterror agent, it was selected as a model for further in vitro characterization of rafts in PB. In silico and in vitro analysis showed significant similarity of FlotP with numerous attributes of Flotillin-1. Its punctate distribution on membrane with exclusive localization in detergent resistant membrane fraction; strongly favors presence of raft with RMP FlotP in BA. Furthermore, significant effect of Zaragozic acid (ZA), a raft associated lipid biosynthesis inhibitor, on several patho-physiological attributes of BA such as growth, morphology, membrane rigidity etc., were also observed. Specifically, a considerable decrease in membrane rigidity, strongly recommended presence of an unknown raft associated lipid molecule on membrane of BA. In addition, treatment with ZA decreased secretion of anthrax toxins and FlotP expression, suggesting potential role of raft in pathogenesis and physiology of BA. Thus, the present study not only suggest the existence and role of raft like entity in pathophysiology of BA but also its possible use for the development of novel drugs or vaccines against anthrax.
Highlights
Eukaryotic plasma membrane harbor small but complex dynamic assemblies of lipids and proteins constituting membrane microdomains, which coordinate membrane signaling and trafficking with raft associated proteins (Bickel et al, 1997; Pike, 2006; Lingwood and Simons, 2010)
Flotillin-1 is a member of SPFH superfamily harboring evolutionary conserved SPFH (Stomatin, Prohibitin, Flotillin, and HflK/C protein) domain which shows affinity for membrane microdomains (Tavernarakis et al, 1999; Zhang et al, 2005; Browman et al, 2007)
Considering the fact that membrane microdomains harbor variety of signaling proteins, it is of utmost interest to investigate presence of such SPFH2a domain harboring proteins in pathogenic bacteria (PB) as a key step toward investigation of membrane microdomains in infectious bacteria
Summary
Eukaryotic plasma membrane harbor small (size ∼10–100 nm) but complex dynamic assemblies of lipids and proteins constituting membrane microdomains (commonly referred to as lipid rafts), which coordinate membrane signaling and trafficking with raft associated proteins (Bickel et al, 1997; Pike, 2006; Lingwood and Simons, 2010). Flotillins have been shown to be involved in scaffolding of DRMs and recruitment of proteins to lipid rafts to facilitate proper interactions, oligomerization, and functioning such as signal transduction, coupling of membranecytoskeleton, and endocytosis (Bickel et al, 1997; Dermine et al, 2001; Krogh et al, 2001; Zhang et al, 2005; López and Kolter, 2010; Zhao et al, 2011; Bach and Bramkamp, 2013) These vital roles of microdomains in membrane organization strongly recommend its need in physiology as well as metabolism
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
