NHBA is processed by kallikrein from human saliva

Abstract

Neisserial Heparin Binding Antigen (NHBA) is a surface-exposed lipoprotein of Neisseria meningitidis and a component of the Bexsero vaccine. NHBA is characterized by the presence of a highly conserved Arg-rich region involved in binding to heparin and heparan sulphate proteoglycans present on the surface of host epithelial cells, suggesting a possible role of NHBA during N . meningitidis colonization. NHBA has been shown to be cleaved by the meningococcal protease NalP and by human lactoferrin (hLF), a host protease presents in different body fluids (saliva, breast milk and serum). Cleavage occurs upstream or downstream the Arg-rich region. Since the human nasopharynx is the only known reservoir of infection, we further investigated the susceptibility of NHBA to human proteases present in the saliva to assess whether proteolytic cleavage could happen during the initial steps of colonization. Here we show that human saliva proteolytically cleaves NHBA, and identified human kallikrein 1 (hK1), a serine protease, as responsible for this cleavage. Kallikrein-related peptidases (KLKs) have a distinct domain structure and exist as a family of 15 genes which are differentially expressed in many tissues and in the central nervous system. They are present in plasma, lymph, urine, saliva, pancreatic juices, and other body fluids where they catalyze the proteolysis of several human proteins. Here we report the characterization of NHBA cleavage by the tissue kallikrein, expressed in saliva and the identification of the cleavage site on NHBA both, as recombinant protein or as native protein, when expressed on live bacteria. Overall, these findings provide new insights on NHBA as target of host proteases, highlights thepotential role of NHBA in the Neisseria meningitidis nasopharyngeal colonization, and of kallikrein as a defensive agent against meningococcal infection.

Measurement of Bradykinin Formation and Degradation in Blood Plasma: Relevance for Acquired Angioedema Associated With Angiotensin Converting Enzyme Inhibition and for Hereditary Angioedema Due to Factor XII or Plasminogen Gene Variants

“…If the increased KLK-1 kinin formation is confirmed in additional HAE-PLG patients and independent from unknown biases that may affect our sample, a molecular explanation involving the idiosyncratic interaction of the plasminogen pathogenic variant with KLK-1 itself or with its endogenous serpin inhibitor, kallistatin, must be investigated. In the meantime, it is worth noting that the salivary glands are ones of the most KLK-1 rich organs ( https://www.proteinatlas.org/ENSG00000167748-KLK1/tissue ) and that catalytically active KLK-1 is found in human saliva ( 43 ). The clinical presentation of HAE-PLG usually involves the tongues, lips and contiguous areas and a triggering role of salivary KLK-1 is plausible in this context and may be seen in the perspective of local manifestations of a systemic disease ( 44 ).…”

P2 Receptors as Therapeutic Targets in the Salivary Gland: From Physiology to Dysfunction

“…Since the majority of the K + in saliva originates from ductal cells, it has been hypothesized that ATP released from acinar cells during exocytosis stimulates ductal P2X7Rs that regulate the activity of K + channels located on the apical membrane Bhattacharya et al, 2015). In addition to K + modification, activation of P2X7Rs in ductal cells increases phospholipase A2-dependent secretion of arachidonic acid, a precursor of prostaglandin E2 (PGE 2 ), and kallikrein (Alzola et al, 1998) into saliva (Pantano et al, 2019). Interestingly, cell lines of salivary origin exhibit low expression and function of P2X7R, which are enhanced following DNA demethylation (Shin et al, 2015).…”

Serum proteases prevent bacterial biofilm formation: role of kallikrein and plasmin

“…The inhibition of the binding of NHBA and the α-peptide to DNA suggested that FCS affects the integrity of these proteins. Serum contains proteases, such as the C3 convertase of the alternative pathway and PKLK, which have previously been shown to cleave meningococcal NHBA [ 38 , 39 ]. However, these proteolyses should not affect the role of NHBA in biofilm formation as cleavage was shown to occur downstream of the arginine-rich region in this protein leaving an N-terminal fragment with DNA-binding capacity at the cell surface.…”

“…KLK1 and PKLK have preference for Arg-Ser sequences [ 44 ]. Recently, Pantano et al reported that both PKLK and KLK1 cleave NHBA of N. meningitidis strain MC58 [ 39 ]. N-terminal sequencing of the released fragment demonstrated that it starts with a Ser 306 located in the Arg-rich segment [R 298 RS A RS R R S 306 ] ( Figure 1 ).…”