Human Biliverdin Reductase Suppresses Goodpasture Antigen-binding Protein (GPBP) Kinase Activity

Abstract

The Ser/Thr/Tyr kinase activity of human biliverdin reductase (hBVR) and the expression of Goodpasture antigenbinding protein (GPBP), a nonconventional Ser/Thr kinase for the type IV collagen of basement membrane, are regulated by tumor necrosis factor (TNF-␣). The pro-inflammatory cytokine stimulates kinase activity of hBVR and activates NF-B, a transcriptional regulator of GPBP mRNA. Increased GPBP activity is associated with several autoimmune conditions, including Goodpasture syndrome. Here we show that in HEK293A cells hBVR binds to GPBP and down-regulates its TNF-␣-stimulated kinase activity; this was not due to a decrease in GPBP expression. Findings with small interfering RNA to hBVR and to the p65 regulatory subunit of NF-B show the hBVR role in the initial stimulation of GPBP expression by TNF-␣-activated NF-B; hBVR was not a factor in mediating GPBP mRNA stability. The interacting domain was mapped to the 281 CX 10 C motif in the C-terminal 24 residues of hBVR. A 7-residue peptide, KKRILHC 281 , corresponding to the core of the consensus D(␦)-Box motif in the interacting domain, was as effective as the intact 296-residue hBVR polypeptide in inhibiting GPBP kinase activity. GPBP neither regulated hBVR expression nor TNF-␣ dependent NF-B expression. Collectively, our data reveal that hBVR is a regulator of the TNF-␣-GPBP-collagen type IV signaling cascade and uncover a novel biological interaction that may be of relevance in autoimmune pathogenesis. Goodpasture syndrome (GPS)2 is a disorder mediated by autoantibody attack against the C-terminal noncollagenous-1 (NC1) domain of the ␣3 chain of the type IV collagen of basement membrane (␣3(IV)NC1) (Goodpasture antigen (GPA)). The NC1 domain initiates the braiding of the collagenous domains into a triple helical structure (protomer) and then mediates the assembly of two individual protomers yielding a quaternary structure known as the hexamer. The autoantibody epitope is cryptic in the hexamer, and the mechanism for its immunological exposure remains unknown. The autoimmune reaction results in deposits of autoantibodies along alveolar and glomerular basement membranes, causing lung hemorrhage and rapidly progressive glomerulonephritis, the two cardinal clinical manifestations of GPS (1, 2).Goodpasture antigen-binding protein (GPBP) is a nonconventional TNF-␣-inducible Ser/Thr kinase that targets the ␣3(IV)NC1 domain and regulates basement membrane collagen organization (3-6). Cells express at least two GPBP isoforms of 77 and 91 kDa. The 77-kDa GPBP polypeptide (GPBP in this report) interacts with type IV collagen, whereas the 91-kDa isoform associates with the cellular membrane and regulates extracellular levels of the 77-kDa polypeptide (7). In the present study we concentrated on the interaction of hBVR with the 77-kDa form of GPBP by transfecting cells with an expression plasmid encoding this form and using the cytoplasmic fraction of the cell lysate; hBVR is a soluble protein. GPBP phosphorylates GPA at its N terminus (6). Alterations in protein phosp...

Characterization of the human biliverdin reductase gene structure and regulatory elements: promoter activity is enhanced by hypoxia and suppressed by TNF‐α‐activated NF‐κB

“…This finding suggests that hBVR itself mediates the activation of NF‐κB in the pathway. We also obtained 12 clones in this screen for the Goodpasture antigen binding protein, and we have confirmed that interaction by several independent criteria (61).…”

The Human Biliverdin Reductase-based Peptide Fragments and Biliverdin Regulate Protein Kinase Cδ Activity

“…1e. Moreover, based on our previous study with another hBVRinteractive kinase, Goodpasture antigen-binding protein, an atypical protein kinase (57,58), it is plausible that the C-terminal segment of hBVR is involved in interaction with the Zn The Ser/Thr residues in RXX(S/T) and its related motif RXRXX(S/T) are phosphorylation targets of PKC␦, as well as CaMK2 and PKB/Akt (34,36,37). The identified substrate peptide, GLKRNRYLSFHFK, presents a new type of substrate for the PKC, and it shares with the previously identified substrates, FIGURE 6.…”

“…The products were separated by gel electrophoresis and detected by autoradiography. The loading for each sample was estimated by probing the blot with anti-BVR antibody, after first allowing radioactivity to decay (7,58).…”

Biliverdin reductase: a target for cancer therapy?

“…There is also some evidence for BVR playing an indirect role in he development of autoimmunity. A yeast two-hybrid assay using BVR as the bait revealed that the Goodpasture antigen-binding protein (GPBP) was a high affinity binding partner ( Miralem et al, 2010 ). Goodpasture syndrome is one of several autoimmune diseases in which GPBP activity is increased, and is characterized by autoimmune recognition of the C-terminal non-collagenous-1 domain of the α3 chain of type IV collagen (Goodpasture antigen) in epithelial basement membranes.…”