Cellular Up-regulation of Nedd4 Family Interacting Protein 1 (Ndfip1) using Low Levels of Bioactive Cobalt Complexes

Abstract

The delivery of metal ions using cell membrane-permeable metal complexes represents a method for activating cellular pathways. Here, we report the synthesis and characterization of new [ Transition metals are essential for many important chemical processes in biological systems. Most of these metal-related processes occur by interactions with nucleic acids and proteins. Within the cell, metal ions can stabilize, destabilize, or modulate DNA and proteins by introducing conformational changes and by creating centers of activity. Although the use of metals as structural elements within the cell is well known, emerging evidence now recasts metals as signaling molecules able to activate critical cellular pathways. For example, metals such as iron, copper, and cobalt can produce reactive oxygen species that lead to the activation of redox-sensitive transcription factors including NF-B, AP-1, and p53. Metals have also been suggested to affect the upstream regulatory components of the MAP kinase and the PI3K/Akt/mTor pathway (1, 2). Thus the levels and regulation of metals in a cell can have a direct role on cell function and survival.Metal ions such as Co II and Fe II can stimulate the expression of the neuroprotective protein Nedd4 family interacting protein 1 (Ndfip1) 4 in the brain (3). Ndfip1 is a transmembrane protein that is localized to the Golgi and post-Golgi vesicles such as endosomes (4, 5). Ndfip1 functions as an adaptor protein for the Nedd4 family of ubiquitin ligases that target proteins for both degradation and trafficking (4). The metal-induced up-regulation of Ndfip1 results in the activation of the ubiquitin proteasome pathway. Ndfip1 recognizes and interacts with divalent metal transporter 1 (DMT1), this recruits the E3 ligase Nedd4 -2 resulting in degradation of DMT1, preventing iron overload within the cell (3). Other targets for Ndfip1 have also been identified, including the transcription factor JunB that is regulated by Ndfip1 in association with the E3 ligase Itch (6). In the adult brain, Ndfip1 is endogenously present in cortical neurons at low levels, however it is up-regulated in a subset of neurons upon activation by injury or stress (7). Importantly, this up-regulation of Ndfip1 has been shown to be neuroprotective, and neurons with up-regulated Ndfip1 do not undergo apoptosis.Whereas high levels of exogenous Co II and Fe II are toxic to cells, our previous results show they also stimulate Ndfip1 via still unknown mechanisms. Barring the effects of metal toxicity, this finding introduces an opportunity to harness the capacity of metal ions to up-regulate Ndfip1 for neuroprotective purposes. In the present study, we investigate the utility of nontoxic metal complexes for controlled intracellular delivery of cobalt to stimulate Ndfip1 expression. This was based on the premise that the reactivity of metal ions can be modulated by the formation of coordination complexes, with a complexed 4 The abbreviations used are: Ndfip1, Nedd4 family interacting protein 1; DMT1, divalent metal transporte...

Synthesis of Homochiral CoIII– and MnIV–[2.2]Paracyclophane Schiff Base Complexes with Predetermined Chirality at the Metal Centre

“…The X‐ray structure also showed that the complex had recrystallised as a single enantiomer. As expected, the metal ion has a distorted octahedral environment, and the Co–N1 [1.903(7) Å] and Co–O1 [1.865(5) Å] bond lengths are similar to those found in a comparable Co III (L)acac complex with a simple Schiff base ligand …”

Increased Ndfip1 in the Substantia Nigra of Parkinsonian Brains Is Associated with Elevated Iron Levels

“…Ndfip1 can be upregulated in response to extracellular stress such as hypoxia or metal toxicity [4], [5], and this activation results in the regulation of a number of critical proteins such as DMT1. Previously we have observed that in an environment where metal concentrations are elevated, Ndfip1 is upregulated by a mechanism that does not require either HSP70 or HIF-1α response [28], and resulted in the binding and degradation of DMT1 [5]. It should be noted that DMT1 abundance can also be regulated transcriptionally and differential expression of DMT1 isoforms having been observed due to iron exposure [10], hypoxia [29] and NFκB activation [30].…”

Effects of tethered ligands and of metal oxidation state on the interactions of cobalt complexes with the 26S proteasome

“…Unlike the previously studied inert 3 d 8 nickel(II) ion, cobalt(III) is a redox-active species capable of being reduced to cobalt(II) within the reducing cellular environment by available reductants. This reduction has been demonstrated individually by several groups [12,13] and utilized for release of alkylating agents such as nitrogen mustards. The redox potential for the cytosolic environment is reported to be around −0.3 V vs. NHE by Østegaard [32].…”

“…The antitumor activity of cobalt species is fairly understudied, [10] but activity against prostate cancer has been recently demonstrated by McNail et al for bivalent cobalt. [11] On the other hand, Teicher, Ware, Hambley, [12] and more recently Donelly [13] have taken advantage of bioreductive activation of its trivalent counterpart for the treatment of hypoxic tumors. In this case, intracellular redox conversion of Co(III) into Co(II) releases alkylating mustards.…”