Disease relevance of Lcp1

• Inhibition of the NKp30 activating receptor by pp65 of human cytomegalovirus [1].
• Notably, target cells that either expressed full-length pp65 protein from vaccinia viruses or were sensitized with the CTL epitope encoded in the vaccine were recognized by splenic effectors from immunized animals [2].
• These results suggested that overexpression of L-plastin might be functionally involved in prostate cancer invasion and metastasis, and raised the possibility that L-plastin gene-specific antisense delivery could potentially be a useful approach to interfere with prostate cancer progression in vivo [3].
• In contrast to this block in virion infectivity, cell-to-cell transfer of pp65-containing particles was observed, suggesting that release of dense bodies continued in the absence of pp150 [4].
• Finally, female NZB/W F1 mice immunized with plasmids encoding HCMV pp65 open reading frame (pcDNApp65) developed an early onset of autoantibody activity and more severe glomerulonephritis [5].

High impact information on Lcp1

• Thus, pp65 is a ligand for the NKp30 receptor and demonstrates a unique mechanism by which an intracellular viral protein causes general suppression of natural killer cell cytotoxicity by specific interaction with an activating receptor [1].
• Single antigen rMVA expressing pp65 or IE1, either ubiquitin-modified or native, stimulated both cytotoxic T lymphocyte (CTL) populations to be expanded up to 500-fold in a 60-mL blood draw from the same donor [6].
• In this context, we have inserted full-length and ubiquitin-modified CMV phosphoprotein 65 (pp65), phosphoprotein 150 (pp150), and immediate early protein 1 (IE1) immunodominant antigens into the virulent Western Reserve strain of vaccinia virus (VV) and the highly attenuated strain, modified vaccinia Ankara (MVA) [6].
• Based on the finding that gene expression for the actin-bundling protein L-plastin is inducible by androgen and that L-plastin is overexpressed in malignant epithelium of the prostate, we examined the functional consequences of L-plastin down-regulation in prostate carcinoma cell lines by both transfection and retroviral infection [3].
• The antisense construct for the 5'-untranslated region with the most unique sequence for the L-plastin gene was more effective in down-regulation efficiency compared with the larger antisense construct in the coding region, which maintains homology to other members of the plastin gene family [3].

Chemical compound and disease context of Lcp1

• Parenteral injection of a lipopeptide containing a human leucocyte antigen (HLA)-A*0201-restricted cytotoxic T-lymphocyte (CTL) epitope from the human cytomegalovirus (HCMV) immunodominant matrix protein pp65 efficiently induces systemic CTL responses in HLA-A*0201 transgenic mice [7].

Biological context of Lcp1

• From the amino acid sequence of the dodecapeptide Gly-Ser-Val-Ser-Asp-Glu-Glu-Met-Met-Glu-Leu-Arg, the phosphorylation site of pp65 was located at the N-terminal region adjacent to the first Ca2+ binding domain [8].
• In the present study, the complete primary structure of pp65 was determined on the basis of the cDNA containing an open reading frame of 1881 bases [8].
• T- and I-fimbrin expression could be critical for the formation and extension of the microvilli whereas L-fimbrin may play a role in controlling cell adhesion [9].
• Because L-plastin expression in tissue-specifically regulated in both humans and rodents, it is likely that similar mechanisms regulate L-plastin gene expression in human and rodent cells and that they could be identified by comparing the function and nucleotide sequences of the human and murine L-plastin gene promoters [10].
• Preliminary proteomic analysis of protein S-nitrosothiols has identified elongation factor 2, heat shock protein 90 beta, and a 65-kDa macrophage protein homologous to human L-plastin as major nitrosation targets at high intracellular nitrosation levels in the murine macrophage-derived RAW 264.7 cell line [11].

Anatomical context of Lcp1

• We previously isolated a 65-kDa cytosolic protein (pp65) that was phosphorylated specifically in LPS-stimulated murine macrophages [8].
• In response to stimulation, L-fimbrin accumulated and co-localized with Iba1 in membrane ruffles induced by M-CSF-stimulation and phagocytic cups formed by IgG-opsonized beads in microglial cell line MG5 [12].
• I-fimbrin is expressed by intestine and kidney epithelial cells, L-fimbrin is expressed by leukocytes and many tumors, while T-fimbrin is expressed by various cells and tissues [9].
• L-fimbrin was also detected during this period but it was localized to the basal surface of the epithelium instead of the apical surface [9].
• Immunogenicity evaluation indicates that pp65-IE1-MVA not only can induce robust primary CMI to both antigens in HLA A2.1 Tg mice, but also can stimulate vigorous expansion of memory T lymphocyte responses to pp65 and IE1 in PBMC of CMV-positive donors [13].

Associations of Lcp1 with chemical compounds

• Complete primary structure and phosphorylation site of the 65-kDa macrophage protein phosphorylated by stimulation with bacterial lipopolysaccharide [8].
• By using purified proteins, direct binding of Iba1 to L-fimbrin was demonstrated by immunoprecipitation, glutathione S-transferase pull-down assays and ligand overlay assays [12].
• Replacing alpha69 alanine with threonine, valine or serine completely eliminated the ability to stimulate autoreactive T-cell clones without affecting the ability to present foreign antigen keyhole limpet haemocyanin (KLH) or L-plastin peptide to specific T-cell clones [14].
• Our results indicate multiple unique proteins not previously identified as S-nitrosylation targets: enolase, pyruvate kinase, elongation factor-1 and -2, plastin-2, FRAG-6, CEM-16, and SMC-6 [15].

Other interactions of Lcp1

• The sequence of pp65 revealed that it is a murine homologue of human L-plastin, recently identified as a novel transformation-induced polypeptide of neoplastic human cells, and that it contains a unique series of Ca2+, calmodulin, and actin binding domains [8].

Analytical, diagnostic and therapeutic context of Lcp1

• A single phosphorylated peptide was isolated from the tryptic digest of pp65 by reverse-phase HPLC [8].
• One of the antibodies, p65-7B5, was demonstrated to react to native p65/L-plastin by Western blot, flow cytometric, and immunohistochemical analysis [16].
• Western blot analysis of isolated nuclei and indirect immunofluorescence experiments indicated that pp71, like the major tegument protein pp65, is present in the nucleus shortly after infection as well as during the late phase of viral morphogenesis [17].
• Epitope mapping to date has mainly focused on the pp65 antigen but other antigens such as IE1 are starting to be mapped [18].
• Mice immunized with the pp65 plasmid developed pp65-specific cytotoxic T lymphocytes (CTL) and ELISA antibodies [19].

References