A defensin from clam Venerupis philippinarum: Molecular characterization, localization, antibacterial activity, and mechanism of action

Abstract

A B S T R A C TAntimicrobial peptides (AMPs) are important mediators of the primary host defense system against microbial invasion. In the present study, we cloned and characterized a member of the invertebrate defensin from the clam Venerupis philippinarum, designated VpDef. Amino acid sequence analysis showed that VpDef was similar to defensins from marine mollusks and ticks. In non-stimulated clams, RT-PCR and immunohistochemical analysis revealed that both VpDef mRNA and the encoding peptide were constitutively expressed in hemocytes and mantles, as well as in other major tissues. VpDef transcripts were significantly induced in hemocytes at different time intervals post Vibrio anguillarum infection. The recombinant VpDef (rVpDef) showed the highest activity against Gram-positive bacteria Micrococcus luteus and less effective to Gram-negative bacteria. In addition, incubation of rVpDef with M. luteus at 1 × and 3 × MIC could induce an obvious decrease of the membrane potential and notable changes of membrane permeability in a dose-dependent manner. Membrane integrity and bacterial viability analysis also revealed that rVpDef increased the membrane permeability of M. luteus and then resulted in cell death at 2 × and 10 × MIC. Overall, these results suggest that VpDef has an important function in host defense against invasive pathogens, probably killing microbes by inducing membrane lesions.

Recombinant Expression of a Modified Shrimp Anti-Lipopolysaccharide Factor Gene in Pichia pastoris GS115 and Its Characteristic Analysis

“…In the present study, mFcALF2 has been proven to destroy the bacterial cell membrane, and lead to the leakage of the cytoplasm from bacteria. This is very similar to that of the reported ALF isoforms without any modification [39] and other AMPs [40]. Different from the traditional antibiotics, which have specific molecular targets, mFcALF2 might function by binding to the cell membrane of the bacteria through physical process, which is similar to that for other AMPs [41].…”

Structure and Bioactivity of a Modified Peptide Derived from the LPS-Binding Domain of an Anti-Lipopolysaccharide Factor (ALF) of Shrimp

“…In the present study, the biological characteristics of LBDv were analyzed. LBDv peptide could kill both Gram-negative bacteria E. coli and Gram-positive bacteria S. epidermidis at short time as other AMPs like defensin [ 32 ]. The LBDv peptide could bind to bacteria directly, which is in accordance with previous reports that LBD peptide of ALF shows a high affinity to lipopolysaccharide (LPS) and lipoteichoic acid (LA) [ 33 ].…”

Scavenger receptor class B type I (SR-BI) in Ruditapes philippinarum: A versatile receptor with multiple functions

“…Bacterial challenge experiment was performed according to our previous study [12]. Briefly, 300 clams were randomly divided into three treatments and kept in nine aerated tanks (50 L).…”

“…The tissue distribution of RpSR-BI transcripts was analyzed in an Applied Biosystem 7500 Real-time PCR System. The RNA extraction, cDNA synthesis and quantitative PCR analysis were performed according to previously described [12]. Briefly, total RNAs from hemocytes, mantle, gills, hepatopancreas and adductor muscle were extracted from six individuals using Trizol reagent (Invitrogen, USA).…”