LAV-BPIFB4 isoform modulates eNOS signalling through Ca2+/PKC-alpha-dependent mechanism

Abstract

AimsAgeing is associated with impairment of endothelial nitric oxide synthase (eNOS) and progressive reduction in endothelial function. A genetic study on long-living individuals—who are characterized by delays in ageing and in the onset of cardiovascular disease—previously revealed I229V (rs2070325) in bactericidal/permeability-increasing fold-containing-family-B-member-4 (BPIFB4) as a longevity-associated variant (LAV); the LAV protein enhanced endothelial NO production and vasorelaxation through a protein kinase R–like endoplasmic reticulum kinase/14-3-3/heat shock protein 90 signal. Here, we further characterize the molecular mechanisms underlying LAV-BPIFB4-dependent enhancement of vascular function.Methods and resultsLAV-BPIFB4 upregulated eNOS function via mobilization of Ca2+ and activation of protein kinase C alpha (PKCα). Indeed, the overexpression of LAV-BPIFB4 in human endothelial cells enhanced ATP-induced Ca2+ mobilization and the translocation of PKCα to the plasma membrane. Coherently, pharmacological inhibition of PKCα blunted the positive effect of LAV-BPIFB4 on eNOS and endothelial function. In addition, although LAV-BPIFB4 lost the ability to activate PKCα and eNOS in ex vivo vessels studied in an external Ca2+-free medium and in vessels from eNOS−/− mice, it still potentiated endothelial activity, recruiting an alternative mechanism dependent upon endothelium-derived hyperpolarizing factor (EDHF).ConclusionsWe have identified novel molecular determinants of the beneficial effects of LAV-BPIFB4 on endothelial function, showing the roles of Ca2+ mobilization and PKCα in eNOS activation and of EDHF when eNOS is inhibited. These results highlight the role LAV-BPIFB4 can have in restoring signals that are lost during ageing.

New Insights for BPIFB4 in Cardiovascular Therapy

“…Moreover, LAV-BPIFB4 is phosphorylated by protein kinase C alpha (PKCα) in Ser75, which activates calcium mobilization, which in turn determines PKCα activation, generating a feed-forward mechanism. ( Figure 1 ) [ 24 ].…”

“…In a mouse model of ATS (i.e., ApoE knockout mice fed a high fat diet), LAV-BPIFB4 is able to restore acetylcholine-mediated endothelial vasorelaxation in mesenteric and femoral arteries. Furthermore, increased expression and end phosphorylation status at Ser75 of BPIFB4 have been observed in the mesenteric artery [ 24 ]. In a similar way LAV-BPIFB4 is able to induce eNOS phosphorylation at Ser1177 and PKCα phosphorylation at Thr497 ( Figure 1 ) [ 24 ].…”

“…Furthermore, increased expression and end phosphorylation status at Ser75 of BPIFB4 have been observed in the mesenteric artery [ 24 ]. In a similar way LAV-BPIFB4 is able to induce eNOS phosphorylation at Ser1177 and PKCα phosphorylation at Thr497 ( Figure 1 ) [ 24 ]. In particular, eNOS is a key factor for CXCL12/CXC-chemokine receptor 4 (CXCR4)-mediated endothelial actions, as well as different PKC isoforms can mediate CXCR4 phosphorylation and activation [ 61 ].…”

A Model of Evolutionary Selection: The Cardiovascular Protective Function of the Longevity Associated Variant of BPIFB4

“…A more recent study, aimed at understanding the molecular players involved in BPIFB4 protective action, showed that the LAV isoform acts by increasing calcium mobilization through the phosphorylation of protein kinase C alpha (PKCα) [ 53 ]. LAV-BPIFB4, indeed, enhances PKCα translocation to the membrane, a crucial step for its activation.…”

“…LAV-BPIFB4, indeed, enhances PKCα translocation to the membrane, a crucial step for its activation. Furthermore, BPIFB4 contains a phosphorylation site (Ser 75) for PKCα that in turn is activated by LAV-BPIFB4 through calcium mobilization [ 53 ]. Consistently, LAV-BPIFB4 loses its protective role in the absence of extracellular calcium.…”