Pyridoxamine protects proteins from functional damage by 3-deoxyglucosone: mechanism of action of pyridoxamine

Pyridoxamine (PM) is a promising drug candidate for treatment of diabetic nephropathy. The therapeutic effect of PM has been demonstrated in multiple animal models of diabetes and in phase II clinical trials. However, the mechanism of PM therapeutic action is poorly understood. One potential mechanism is scavenging of pathogenic reactive carbonyl species (RCS) found to be elevated in diabetes. We have suggested previously that the pathogenicity of RCS methylglyoxal (MGO) may be due to modification of critical arginine residues in matrix proteins and interference with renal cell-matrix interactions. We have also shown that this MGO effect can be inhibited by PM (Pedchenko et al. (2005) Diabetes 54, 2952-2960). These findings raised the questions of whether the effect is specific to MGO, whether other structurally different physiological RCS can act via the same mechanism, and whether their action is amenable to PM protection. In the present study, we have shown that the important physiological RCS 3-deoxyglucosone (3-DG) can damage protein functionality, including the ability of collagen IV to interact with glomerular mesangial cells. We have also demonstrated that PM can protect against 3-DG-induced protein damage via a novel mechanism that includes transient adduction of 3-DG by PM followed by irreversible PM-mediated oxidative cleavage of 3-DG. Our results suggest that, in diabetic nephropathy, the therapeutic effect of PM is achieved, in part, via protection of renal cell-matrix interactions from damage by a variety of RCS. Our data emphasize the potential importance of the contribution by 3-DG, along with other more reactive RCS, to this pathogenic mechanism.     

Goodpasture antigen-binding protein and its spliced variant, ceramide transfer protein, have different functions in the modulation of apoptosis during zebrafish development

Human Goodpasture antigen-binding protein (GPBP) is an atypical protein kinase that phosphorylates the Goodpasture auto-antigen, the alpha3 chain of collagen IV. The COL4A3BP gene is alternatively spliced producing two protein isoforms: GPBP and GPBPDelta26. The latter lacks a serine-rich domain composed of 26 amino acid residues. Both isoforms also function as ceramide transfer proteins (CERT). Here, we explored the function of Gpbp and GpbpDelta26/CERT during embryogenesis in zebrafish. We cloned both splice variants of the zebrafish gene and found that they are differentially expressed during development. We used antisense oligonucleotide-mediated loss-of-function and synthetic mRNA-based gain-of-function approaches. Our results show that the loss-of-function phenotype is linked to cell death, evident primarily in the muscle of the somites, extensive loss of myelinated tracks, and brain edema. These results indicate that disruption of the nonvesicular ceramide transport is detrimental to normal embryonic development of somites and brain because of increased apoptosis. Moreover, this phenotype is mediated by Gpbp but not GpbpDelta26/CERT, suggesting that Gpbp is an important factor for normal skeletal muscle and brain development.     

A new series of neutral 5-substituted 4-anilinoquinazolines as potent, orally active inhibitors of erbB2 receptor tyrosine kinase

Starting from initial lead 1 containing a basic 5-substituent, optimisation of the glycolamide-derived neutral 5-substituent led to potent inhibitors of erbB2 with good pharmacokinetics. Representative compounds 19 and 21 inhibited phosphorylation of erbB2 in a mouse BT474C xenograft model after oral administration.     

Discovery of a potent, selective, and less flexible selective norepinephrine reuptake inhibitor (sNRI)

The design, synthesis, and SAR of a series of ring-constrained norepinephrine reuptake inhibitors are described. A substantially rigid inhibitor with potent functional activity at the transporter (IC₅₀ = 8 nM) was used to develop a model for the distance and orientation of key features necessary for interaction with the norepinephrine transporter (NET).     

Molecular and genetic analysis of condensin function in vertebrate cells

We engineered mutants into residues of SMC2 to dissect the role of ATPase function in the condensin complex. These residues are predicted to be involved in ATP binding or hydrolysis and in the Q-loop, which is thought to act as a mediator of conformational changes induced by substrate binding. All the engineered ATPase mutations resulted in lethality when introduced into SMC2 null cells. We found that ATP binding, but not hydrolysis, is essential to allow stable condensin association with chromosomes. How SMC proteins bind and interact with DNA is still a major question. Cohesin may form a ring structure that topologically encircles DNA. We examined whether condensin behaves in an analogous way to its cohesin counterpart, and we have generated a cleavable form of biologically active condensin with PreScission protease sites engineered into the SMC2 protein. This has allowed us to demonstrate that topological integrity of the SMC2-SMC4 heterodimer is not necessary for the stability of the condensin complex in vitro or for its stable association with mitotic chromosomes. Thus, despite their similar molecular organization, condensin and cohesin exhibit fundamental differences in their structure and function.     

A "glyconutrient sham"

The discipline of glycobiology contributes to our understanding of human health and disease through research, most of which is published in peer-reviewed scientific journals. Recently, legitimate discoveries in glycobiology have been used as marketing tools to help sell plant extracts termed "glyconutrients." The glyconutrient industry has a worldwide sales force of over half a million people and sells nearly half a billion dollars (USD) of products annually. Here we address the relationship between glyconutrients and glycobiology, and how glyconutrient claims may impact the public and our discipline.     

Endocrine late effects of childhood cancer therapy: a report from the Children's Oncology Group

Pediatric oncologists are curing increasing numbers of patients with childhood cancer, and most children diagnosed with a malignancy may now be expected to become long-term survivors. As the number of childhood cancer survivors grows, so too does the need for evidence-based surveillance of the long-term effects of cancer therapy. Long-term effects involving the endocrine system represent a frequent complication of therapy. The Children's Oncology Group Long-Term Follow-Up Guidelines for Survivors of Childhood, Adolescent, and Young Adult Cancers(COG LTFUG), most recently updated in 2006, provide a summary of the known endocrine late effects of surgery, radiation, chemotherapy, and stem cell transplant. This paper summarizes the scope and nature of the endocrine late effects of childhood cancer therapy based upon a review of the pertinent medical literature, and demonstrates how pediatric oncologists can use these guidelines in clinical practice.     

Pattern recognition based on color-coded quantum mechanical surfaces for molecular alignment

A pattern recognition algorithm for the alignment of drug-like molecules has been implemented. The method is based on the calculation of quantum mechanical derived local properties defined on a molecular surface. This approach has been shown to be very useful in attempting to derive generalized, non-atom based representations of molecular structure. The visualization of these surfaces is described together with details of the methodology developed for their use in molecular overlay and similarity calculations. In addition, this paper also introduces an additional local property, the local curvature (C _L), which can be used together with the quantum mechanical properties to describe the local shape. The method is exemplified using some problems representing common tasks encountered in molecular similarity. Figure Molecular surfaces for Lorazepam (left) and Diazepam (right)