Zinc Binding Sites Conserved in Short Neuropeptides Containing a Diphenylalanine Motif

What Is the Correlation between Preeclampsia and Cancer? The Important Role of Tachykinins and Transition Metal Ions

Metal ions are irreplaceable in many biological processes. They are components of numerous metalloproteins and serve as cofactors or structural elements for enzymes. Interestingly, iron, copper and zinc play important roles in accelerating or preventing neoplastic cell transformation. Noteworthily, a lot of proliferative and invasive mechanisms are exploited by both malignant tumors and pregnancy. Cancer cells, as well as developing placenta cells, create a microenvironment supportive of immunologic privilege and angiogenesis. Therefore, pregnancy and cancer progression share many similarities. Moreover, during preeclampsia and cancer, significant changes in relevant trace element concentrations, tachykinin levels, expressions of neurokinin receptors, oxidative stress and angiogenic imbalance are observed. This sheds a new light on the role of metal ions and tachykinins in cancer progression and pregnancy, especially in preeclamptic women.

Poly-Gly Region Regulates the Accessibility of Metal Binding Sites in Snake Venom Peptides

It is supposed that the presence of poly-His regions in close proximity to poly-Gly domains in snake venoms is related to their biological activity; poly-His/poly-Gly (pHpG) peptides inhibit the activity of metalloproteinases during venom storage via the chelation metal ions, necessary for their proper functioning. This work shows that only the histidyl residues from the N-terminal VDHDHDH motif (but not from the poly-His tag) were the primary Zn(II) binding sites and that the poly-Gly domain situated in the proximity of a central proline residue may play a regulatory role in venom gland protection. The proline induces a kink of the peptide, resulting in steric hindrance, which may modulate the accessibility of potential metal binding sites in the poly-His domain and may, in turn, be one of the regulators of Zn(II) accessibility in the venom gland and therefore a modulator of metalloproteinase activity during venom storage.

The proline induces a kink of the peptide, resulting in a steric hindrance, which may modulate the accessibility of potential metal binding sites in the poly-His domain and may, in turn, be one of the regulators of Zn(II) accessibility in the venom gland and therefore a modulator of metalloproteinase activity during venom storage.

Neuropeptides: Roles and Activities as Metal Chelators in Neurodegenerative Diseases

Neurodegenerative diseases, such as Alzheimer's disease (AD) and Parkinson's disease (PD), are characterized by deposits of amyloid proteins. The homeostasis of metal ions is crucial for the normal biological functions in the brain. However, in AD and PD, the imbalance of metal ions leads to formation of amyloid deposits. In the past four decades, there has been extensive effort to design compound agents than can chelate metal ions with the aim of preventing the formation of the amyloid deposits. Unfortunately, the compounds to date that were designed were not successful candidates to be used in clinical trials. Neuropeptides are small molecules that are produced and released by neurons. It has been shown that neuropeptides have neuroprotective effects in the brain and reduce the formation of amyloid deposits. This Review Article is focused on the function of neuropeptides as metal chelators. Experimental and computational studies demonstrated that neuropeptides could bind metal ions, such as Cu²⁺ and Zn²⁺. This Review Article provides perspectives and initiates future studies to investigate the role of neuropeptides as metal chelators in neurodegenerative diseases.

Proteostasis of Islet Amyloid Polypeptide: A Molecular Perspective of Risk Factors and Protective Strategies for Type II Diabetes

The possible link between hIAPP accumulation and β-cell death in diabetic patients has inspired numerous studies focusing on amyloid structures and aggregation pathways of this hormone. Recent studies have reported on the importance of early oligomeric intermediates, the many roles of their interactions with lipid membrane, pH, insulin, and zinc on the mechanism of aggregation of hIAPP. The challenges posed by the transient nature of amyloid oligomers, their structural heterogeneity, and the complex nature of their interaction with lipid membranes have resulted in the development of a wide range of biophysical and chemical approaches to characterize the aggregation process. While the cellular processes and factors activating hIAPP-mediated cytotoxicity are still not clear, it has recently been suggested that its impaired turnover and cellular processing by proteasome and autophagy may contribute significantly toward toxic hIAPP accumulation and, eventually, β-cell death. Therefore, studies focusing on the restoration of hIAPP proteostasis may represent a promising arena for the design of effective therapies. In this review we discuss the current knowledge of the structures and pathology associated with hIAPP self-assembly and point out the opportunities for therapy that a detailed biochemical, biophysical, and cellular understanding of its aggregation may unveil.

Molecular Mechanisms and Aspects on the Role of Neuropeptide Y as a Zn2+ and Cu2+ Chelator

The concept of metal chelation is based on simple coordination chemistry. The development of an ideal metal chelator that completely and selectively removes toxic metals from a specific metal binding site in proteins is required to prevent and or inhibit a variety of diseases, among them neurodegenerative diseases. This work examines neuropeptide Y (NPY) as a Zn²⁺ and Cu²⁺ chelator agent. NPY is a natural peptide that is produced in the human body; therefore, it is not a toxic agent and the complex that it forms is not toxic as well. Our simulations reveal that NPY has an efficient Zn²⁺ chelation activity but is less effective in chelating Cu²⁺. Moreover, while NPY demonstrates several conformations, the metal chelation occurs more efficiently in its native structure. Beyond the exploration of the activity of NPY as a Zn²⁺ and Cu²⁺ chelator agent, this work provides an insight into the molecular mechanisms of the chelation of these metals at the molecular level. The outcomes from this work may guide future experimental studies to examine NPY in metal chelation therapy for neurodegenerative diseases.

Assessments of the Effect of Neurokinin B on Toxic Aβ Aggregates in Alzheimer's Disease with the Molecular Mechanisms' Action

Clinical trials of past and current treatments for Alzheimer's disease (AD) patients on the market suffer from the dual drawbacks of a lack of efficacy and side effects. Neuropeptides have been highlighted by their potential to protect cells against AD and can reverse the toxic effect induced by Aβ in cultured neurons. One of the neuropeptides that has insufficient attention in the literature as a potential treatment for prevention of the progression of AD is neurokinin B (NKB). There are critical and unresolved questions concerning the activation, and the molecular mechanisms underlying NKB effect on prevention of Aβ aggregation remain unknown. The current work identifies for the first time the specific interactions that contribute to the inhibition and prevention of initial seeding of polymorphic early-stage dimers. Three main conclusions are observed in this work. First, NKB inhibits formation of polymorphic early-stage fibrillar Aβ dimers. The efficiency of the inhibition depends on the concentration of NKB (i.e., NKB:Aβ ratio). Second, NKB has an excellent effect of preventing the formation of initial seeding of early-stage nonfibrillar Aβ dimers. Third, NKB peptides may self-assemble to form cross-α fibril-like structure during the inhibition activity of the polymorphic early-stage fibrillar Aβ dimers but not during the prevention activity of early-stage nonfibrillar Aβ dimers. The work provides crucial information for future experimental studies to approve the functional effect of NKB on inhibition and prevention of Aβ polymorphic early-stage oligomers.