Cloning and characterisation of the immunophilin X-CypA in Xenopus laevis

Extracellular and Intracellular Cyclophilin A, Native and Post-Translationally Modified, Show Diverse and Specific Pathological Roles in Diseases

CypA (cyclophilin A) is a ubiquitous and highly conserved protein with peptidyl prolyl isomerase activity. Because of its highly abundant level in the cytoplasm, most studies have focused on the roles of CypA as an intracellular protein. However, emerging evidence suggests an important role for extracellular CypA in the pathogenesis of several diseases through receptor (CD147 or other)-mediated autocrine and paracrine signaling pathways. In this review, we will discuss the shared and unique pathological roles of extracellular and intracellular CypA in human cardiovascular diseases. In addition, the evolving role of post-translational modifications of CypA in the pathogenesis of disease is discussed. Finally, recent studies with drugs specific for extracellular CypA show its importance in disease pathogenesis in several animal models and make extracellular CypA a new therapeutic target.

Molecular identification and expression analysis of a novel cyclophilin a gene in the red swamp crayfish, Procambarus clarkii

Cyclophilin A (Cyp A) is the main intracellular receptor of cyclosporin A (CsA) belonging to the immunophilin family, which is known as an effective immunosuppressive drug. This study aimed to gain insights into the structure and biological function of cyclophilin A in the red swamp crayfish, Procambarus clarkii (PcCypA). We cloned PcCypA by homology cloning and anchored polymerase chain reaction (PCR), and assessed its mRNA and protein expression levels in different tissues using quantitative real-time PCR and western blot analysis, respectively. The full-length DNA contained a 5' untranslated region (UTR) comprising 108 base pairs (bp), an open reading frame of 495 bp encoding a polypeptide of 164 amino acids with an estimated molecular mass of 17.3 kDa, and a 3' UTR of 281 bp including a significant poly(A) plus tail sequence. The predicted amino acid sequence of PcCypA shared high identity with CypA in other organisms. PcCypA transcripts were detected in the hepatopancreas, gill, heart, muscle, testis, and ovary of crayfish, with the highest expression levels in the heart. Western blot analysis found one 17-kDa band in all of the tissues examined, except for the ovary. Molecular identification and expression analysis of PcCypA will facilitate further studies of the immune defense mechanisms in red swamp crayfish, and provide new insights into freshwater invertebrate immunology.

Acetylation of cyclophilin A is required for its secretion and vascular cell activation

AIMS

Cyclophilin A (CyPA) is a pro-inflammatory mediator involved in oxidative stress-related cardiovascular diseases. It is secreted from vascular smooth muscle cell (VSMC) in response to reactive oxygen species (ROS) in a highly regulated manner. Extracellular CyPA activates VSMCs and endothelial cells (ECs) promoting inflammation, cell growth, and cell death. Recently, it was shown that acetylated CyPA (AcK-CyPA) affects its function. We investigated the role of acetylation of CyPA for its secretion and signalling in vascular cells.

METHODS AND RESULTS

We used angiotensin II (Ang II) to create sustained ROS and found significantly increased AcK-CyPA in VSMC. Site-directed mutagenesis showed that lysines K82 and K125 were the predominant CyPA residues acetylated in response to Ang II. Importantly, acetylation of K82 and K125 were required for Ang II-mediated CyPA secretion. ROS inhibitors, Tiron, and N-acetylcysteine inhibited Ang II-induced intracellular CyPA acetylation and also AcK-CyPA secretion. Using secreted CyPA from wild type and K82/125R mutants expressed in transduced VSMC or in vitro acetylated recombinant CyPA, we showed that extracellular AcK-CyPA significantly increased pERK1/2, matrix metalloproteinase-2 activation, and ROS production in VSMC compared with non-acetylated CyPA. Moreover, extracellular AcK-CyPA increased adhesion molecule expression (VCAM-1 and ICAM-1) in EC, which promoted monocyte adhesion.

CONCLUSIONS

ROS-dependent acetylation of CyPA is required for the generation of extracellular CyPA. Acetylated extracellular CyPA regulates VSMC and EC activation, suggesting that inhibition of acetylation of CyPA may prevent the pathogenesis of oxidative stress-related cardiovascular diseases.

Peptidyl-prolyl cis-trans isomerase xFKBP1B induces ectopic secondary axis and is involved in eye formation during Xenopus embryogenesis

Although Xenopus FKBP1A (xFKBP1A) induces an ectopic dorsal axis in Xenopus embryos, involvement of xFKBP1B, a vertebrate paralogue of FKBP1A, in embryogenesis remains undetermined. Here, we demonstrate that xFKBP1B induces ectopic dorsal axis and involves in eye formation of Xenopus embryos. Injection of the xFKBP1B mRNA in ventral blastomeres of 4-cell stage Xenopus embryos induced a secondary axis and showed multiplier effect to that of xFKBP1A on this when xFKBP1A was co-injected. In addition, BMP4 and Smad1 mRNAs did not affect the ability of xFKBP1B to induce the ectopic secondary axis when either was co-injected with xFKBP1B in ventral blastomeres, whereas they downed out that of xFKBP1A, suggesting that xFKBP1A and xFKBP1B induce the ectopic secondary axis through affecting different pathways from each other. On the other hand, the injection of the FKBP1B mRNA in dorsal blastomeres showed eye malformation, and suppressed almost completely the expression of Rx1, Mitf, and Vax2 mRNAs. xFKBP1B was expressed in the dorsal side of the embryo including the eye during embryogenesis at least until stage 46. Injection of morpholino of the xFKBP1B mRNA in dorsal blastomeres induced additional retina or failed to close tapetum nigrum in the ventral side within the optic cap, whereas it did not affect the dorsal organ development. The injection of the morpholino reduced the expression of Xotx2 and Rx1 mRNAs in the eye. These observations suggest that xFKBP1B is a key factor that regulates the expression levels of the genes involved in eye formation during Xenopus embryogenesis.

Identification of a non-mammalian leptin-like gene: characterization and expression in the tiger salamander (Ambystoma tigrinum)

Leptin is well established as a multifunctional cytokine in mammals. However, little is known about the evolution of the leptin gene in other vertebrates. A recently published set of ESTs from the tiger salamander (Ambystoma tigrinum) contains a sequence sharing 56% nucleotide sequence identity with the human leptin cDNA. To confirm that the EST is naturally expressed in the salamander, a 409bp cDNA was amplified by RT-PCR of salamander testis and stomach mRNAs. The coding sequence of the cDNA is predicted to encode 169 amino acids, and the mature peptide to consist of 146 residues, as in mammals. Although the overall amino acid identity with mammalian leptins is only 29%, the salamander and mammalian peptides share common structural features. An intron was identified between coding exons providing evidence that the sequence is present in the salamander genome. Phylogenetic analysis showed a rate of molecular divergence consistent with the accepted view of vertebrate evolution. The pattern of tissue expression of the leptin-like cDNA differed between metamorphosed adult individuals of different sizes suggesting possible developmental regulation. Expression was most prominent in the skin and testis, but was also detected in tissues in which leptin mRNA is present in mammals, including the fat body, stomach, and muscle. The characterization of a salamander leptin-like gene provides a basis for understanding how the structure and functions of leptin have altered during the evolution of tetrapod vertebrates.