The proline rich homeodomain protein PRH/Hhex forms stable oligomers that are highly resistant to denaturation

The Haematopoietically-expressed homeobox transcription factor: roles in development, physiology and disease

The Haematopoietically expressed homeobox transcription factor (Hhex) is a transcriptional repressor that is of fundamental importance across species, as evident by its evolutionary conservation spanning fish, amphibians, birds, mice and humans. Indeed, Hhex maintains its vital functions throughout the lifespan of the organism, beginning in the oocyte, through fundamental stages of embryogenesis in the foregut endoderm. The endodermal development driven by Hhex gives rise to endocrine organs such as the pancreas in a process which is likely linked to its role as a risk factor in diabetes and pancreatic disorders. Hhex is also required for the normal development of the bile duct and liver, the latter also importantly being the initial site of haematopoiesis. These haematopoietic origins are governed by Hhex, leading to its crucial later roles in definitive haematopoietic stem cell (HSC) self-renewal, lymphopoiesis and haematological malignancy. Hhex is also necessary for the developing forebrain and thyroid gland, with this reliance on Hhex evident in its role in endocrine disorders later in life including a potential role in Alzheimer's disease. Thus, the roles of Hhex in embryological development throughout evolution appear to be linked to its later roles in a variety of disease processes.

HM-3-HSA exhibits potent anti-angiogenesis and antitumor activity in hepatocellular carcinoma

HM-3-HSA is an antitumor fusion protein which improved the pharmacokinetics of HM-3. Previous studies reported that HM-3-HSA enhanced antitumor activity of HM-3 in melanoma cells. However, the efficacy and the mechanism of HM-3-HSA in hepatocellular carcinoma, especially its effect on tumor angiogenesis, have not been elucidated. Herein, we showed that HM-3-HSA significantly inhibited the H22 and SMMC-7721 tumor xenografts growth and tumor angiogenesis in vivo, indicating the antitumor activity exerted by HM-3-HSA was closely corrected with its potency on tumor angiogenesis. To investigate the anti-angiogenic mechanism, we evaluated the efficacy of HM-3-HSA in HUVECs in vitro. The results showed that multiple steps of tumor angiogenesis, including endothelial cell proliferation, migration, invasion and tube formation, were substantially inhibited by HM-3-HSA. Mechanism investigations revealed that HM-3-HSA could bind HUVECs via integrin αvβ3 and α5β1 and inhibited phosphorylation of the downstream protein kinases including FAK, Src and PI3 K. Our study was the first to report the activity of HM-3-HSA against hepatocellular carcinoma and tumor angiogenesis as well as the underlying mechanism by which HM-3-HSA to exert its anti-angiogenic activity.

Misregulation of the proline rich homeodomain (PRH/HHEX) protein in cancer cells and its consequences for tumour growth and invasion

The proline rich homeodomain protein (PRH), also known as haematopoietically expressed homeobox (HHEX), is an essential transcription factor in embryonic development and in the adult. The PRH protein forms oligomeric complexes that bind to tandemly repeated PRH recognition sequences within or at a distance from PRH-target genes and recruit a variety of PRH-interacting proteins. PRH can also bind to other transcription factors and co-regulate specific target genes either directly through DNA binding, or indirectly through effects on the activity of its partner proteins. In addition, like some other homeodomain proteins, PRH can regulate the translation of specific mRNAs. Altered PRH expression and altered PRH intracellular localisation, are associated with breast cancer, liver cancer and thyroid cancer and some subtypes of leukaemia. This is consistent with the involvement of multiple PRH-interacting proteins, including the oncoprotein c-Myc, translation initiation factor 4E (eIF4E), and the promyelocytic leukaemia protein (PML), in the control of cell proliferation and cell survival. Similarly, multiple PRH target genes, including the genes encoding vascular endothelial growth factor (VEGF), VEGF receptors, Endoglin, and Goosecoid, are known to be important in the control of cell proliferation and cell survival and/or the regulation of cell migration and invasion. In this review, we summarise the evidence that implicates PRH in tumourigenesis and we review the data that suggests PRH levels could be useful in cancer prognosis and in the choice of treatment options.

Evidence for a role of the polysaccharide capsule transport proteins in pertussis pathogenesis

Polysaccharide (PS) capsules are important virulence determinants for many bacterial pathogens. Bordetella pertussis, the agent of whooping cough, produces a surface associated microcapsule but its role in pertussis pathogenesis remained unknown. Here we showed that the B. pertussis capsule locus is expressed in vivo in murine lungs and that absence of the membrane-associated protein KpsT, involved in the transport of the PS polymers across the envelope, but not the surface-exposed PS capsule itself, affects drastically B. pertussis colonization efficacy in mice. Microarray analysis revealed that absence of KpsT in B. pertussis resulted in global down-regulation of gene expression including key virulence genes regulated by BvgA/S, the master two-component system. Using a BvgS phase-locked mutant, we demonstrated a functional link between KpsT and BvgA/S-mediated signal transduction. Whereas pull-down assays do not support physical interaction between BvgS sensor and any of the capsule locus encoded proteins, absence of KpsT impaired BvgS oligomerization, necessary for BvgS function. Furthermore, complementation studies indicated that instead of KpsT alone, the entire PS capsule transport machinery spanning the cell envelope likely plays a role in BvgS-mediated signal transduction. Our work thus provides the first experimental evidence of a role for a virulence-repressed gene in pertussis pathogenesis.

Ostertagia ostertagi macrophage migration inhibitory factor is present in all developmental stages and may cross-regulate host functions through interaction with the host receptor

Macrophage migration inhibitory factor (MIF) of Ostertagia ostertagi, an abomasal parasite of cattle, was characterised in the present study. Phylogenetic analysis identified at least three O. ostertagi MIFs (Oos-MIFs), each encoded by a distinct transcript: Oos-MIF-1.1, Oos-MIF-1.2 and Oos-MIF-2. Oos-MIF-2 is only distantly related to Oos-MIF-1s, but has higher sequence similarity with the Caenorhabditis elegans MIF2. Oos-MIF-1.1 and Oos-MIF-1.2 are similar (93%) and thus collectively referred to as Oos-MIF-1 when characterised with immunoassays. Recombinant Oos-MIF-1.1 (rOos-MIF-1.1) is catalytically active as a tautomerase. A mutation (rOos-MIF-1.1P1G) or duplication of Pro1 residue (rOos-MIF-1.1P1+P) resulted in reduced oligomerisation and loss of tautomerase activity. The tautomerase activity of rOos-MIF-1.1 was only partially inhibited by ISO-1 but was abrogated by a rOos-MIF-1.1-specific antibody. Oos-MIF-1 was detected in all developmental stages of O. ostertagi, with higher levels in the adult stage; it was also detected in adult worm excretory/secretory product. Oos-MIF-1 was localised to the hypodermis/muscle, reproductive tract and intestine, but not to the cuticle. rOos-MIF-1.1, but not rOos-MIF-1.1P1G, was able to specifically bind to human CD74, a MIF cell surface receptor, with an affinity comparable with human MIF. Immunostaining indicated that macrophages were able to internalise rOos-MIF-1.1, further supporting receptor-mediated transportation. Herein we also show that rOos-MIF-1.1 inhibited migration of bovine macrophages and restored glucocorticoid-suppressed, lipopolysaccharide-induced TNF-α and IL-8 in human and/or bovine macrophages. Given its dual role in self-regulation and molecular mimicry, this secreted parasite protein warrants investigation as a vaccine candidate against O. ostertagi infections in cattle.

Characterization of Neospora caninum macrophage migration inhibitory factor

The present study is the first characterization of Neospora caninum macrophage migration inhibitory factor (NcMIF). BLAST-N analysis of NcMIF revealed high similarity (87%) to the Toxoplasma gondii MIF. NcMIF was cloned and expressed in Escherichia coli in 3 forms, NcMIF (mature protein), NcMIFm (mutation of proline-2 to glycine), and NcMIFhis (addition of a polyhistidine tag at the N-terminus). None of these recombinant NcMIFs (rNcMIF) had tautomerase, oxidoreductase, or immunologic regulatory activities. rNcMIF was unable to compete with recombinant human MIF for a MIF receptor (CD74), suggesting that NcMIF does not bind to this MIF receptor. The glycine substitution for proline-2 of NcMIF resulted in increased retention time on SEC-HPLC and decreased formation of dimers and trimers. The addition of N-terminal HIS-tag led to increased formation of trimers. Immunofluorescence staining demonstrated that NcMIF was localized to the apical end of N. caninum tachyzoites. Immunoelectron microscopy further revealed that NcMIF was present in the micronemes, rhoptries, dense granules, and nuclei. NcMIF was abundant in the tachyzoite lysate and present in excretory and secretory antigen (ESAg) preparations. Total and secretory NcMIF was more abundant in a non-pathologic clone, Ncts-8, than in the wild type isolate (NC1). Furthermore, NcMIF release by the both isolates was increased in the presence of calcium ionophore. This differential production of NcMIF by the pathologic and non-pathologic isolates of N. caninum may suggest a critical role of this molecule in the infectious pathogenesis of this parasite.