Inhibition of Phorbol Ester Binding and Protein Kinase C Activity by Heavy Metals

Speizer, L.A.; Watson, Michael J.; Kanter, Joan R.; Brunton, Laurence L.

doi:10.1016/s0021-9258(18)83586-4

Cited by 65 publications

(4 citation statements)

References 9 publications

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“…For example, Speizer et al. and Rajanna et al have reported that heavy metal ions such as Hg 2+ , Cu 2+ , and Cd 2+ inhibited the enzyme activity of a conventional PKC mixture and its PDBu binding. Thus far, heavy metal ions have been proposed to interact with the catalytic domain of PKC in inhibiting PKC activation. , Our present results strongly indicate that one of the main targets of these heavy metal ions is the C1 domain itself in the regulatory domain.…”

Section: Resultsmentioning

confidence: 99%

“…Modulation of PKC by neurotoxic heavy metals has recently been investigated, since PKC is involved in neurotransmitter release [47][48][49] and signal transduction. 50 For example, Speizer et al 51 and Rajanna et al 52 have reported that heavy metal ions such as Hg 2+ , Cu 2+ , and Cd 2+ inhibited the enzyme activity of a conventional PKC mixture and its PDBu binding. Thus far, heavy metal ions have been proposed to interact with the catalytic domain of PKC in inhibiting PKC activation.…”

Section: Effects Of Metal Ions Other Than Zinc On the Pdbu Binding Of...mentioning

confidence: 99%

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Molecular Basis for Protein Kinase C Isozyme-Selective Binding: The Synthesis, Folding, and Phorbol Ester Binding of the Cysteine-Rich Domains of All Protein Kinase C Isozymes

et al. 1998

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The protein kinase C (PKC) family of enzymes plays a crucial role in cellular signal transduction and tumor promotion. Conventional and novel PKC isozymes consist of a catalytic domain for protein phosphorylation and a regulatory domain which binds the endogenous messenger diacyl glycerol or exogenous agents such as phorbol esters. The N-terminal regulatory region of these isozymes contains two cysteine-rich domains (C1A and C1B, also known as CRD1 and CRD2), both of which are candidates for the phorbol ester-binding site. To determine the phorbol ester-binding sites of these isozymes and to elucidate the structural requirements for isozyme selective PKC modulation, the C1 peptides, consisting of ca. 50 amino acids of all conventional and novel PKCs, along with those of atypical PKCs have been synthesized by a solid - phase Fmoc strategy. Exceptionally high overall yields (10−20%) were achieved in the syntheses of most of the C1 peptides on a Pioneer Peptide Synthesizer (PerSeptive Biosystems) through the use of HATU as a coupling reagent. These peptides were successfully folded by zinc treatment, as monitored by CD spectroscopy. Importantly, only the C1Bs of all conventional and novel PKCs, except for PKCγ, bound [ 3 H]phorbol-12,13-dibutyrate (PDBu) with high affinities, comparable to those of the native isozymes. Of special significance, both C1 peptides of PKCγ (i.e., γ-C1A and γ-C1B) exhibited high-affinity binding, providing the structural basis for a novel approach to PKCγ-selective modulators, compounds of potential significance for the treatment of neuropathic pain. The effects of metal cations other than zinc on the binding of these isozymes were also investigated. Only the PKCγ surrogates (γ-C1A and γ-C1B), when treated with cadmium, exhibited no binding, while other similarly treated conventional and novel PKC surrogates strongly bound PDBu, as did the zinc-folded peptides. These results suggest that cadmium ion could serve as a new and effective tool for controlling the activation of PKCγ.

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Section: Resultsmentioning

confidence: 99%

Section: Effects Of Metal Ions Other Than Zinc On the Pdbu Binding Of...mentioning

confidence: 99%

Molecular Basis for Protein Kinase C Isozyme-Selective Binding: The Synthesis, Folding, and Phorbol Ester Binding of the Cysteine-Rich Domains of All Protein Kinase C Isozymes

et al. 1998

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“…This action of zinc extends not simply to PKC activity , but also affects its translocation, including translocation to the cytoskeleton [ 62 , 63 ]. Of note for the issue of zinc as a micronutrient is that zinc is achieving this PKC regulation at concentrations centering around 50 µM [ 61 , 62 , 63 , 64 ]. This concentration happens to coincide with the levels at which zinc is reported to show efficacy in epithelial barrier function in cell culture models [ 50 , 51 ].…”

Section: A Hypothesis For How Micronutrients At Elevated Levels Are E...mentioning

confidence: 99%

Micronutrients at Supplemental Levels, Tight Junctions and Epithelial Barrier Function: A Narrative Review

DiGuilio,

Del Rio,

Harty

et al. 2024

IJMS

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Disease modifiers, whether from cancer, sepsis, systemic inflammation, or microbial pathogens, all appear to induce epithelial barrier leak, with induced changes of the Tight Junctional (TJ) complex being pivotal to the process. This leak—and the ensuant breakdown of compartmentation—plays a central role in disease morbidity on many levels. Accumulation of lung water in the luminal compartment of airways was a major driver of morbidity and mortality in COVID-19 and is an excellent example of the phenomenon. Increasing awareness of the ability of micronutrients to improve basal barrier function and reduce barrier compromise in pathophysiology may prove to be a low-cost, safe, and easily administered prophylactic and/or therapeutic option amenable to large populations. The growing appreciation of the clinical utility of supplemental doses of Vitamin D in COVID-19 is but one example. This narrative review is intended to propose a general theory on how and why micronutrients—at levels above normal dietary intake—successfully remodel TJs and improve barrier function. It discusses the key difference between dietary/Recommended Daily Allowance (RDA) levels of micronutrients versus supplemental levels, and why the latter are needed in disease situations. It advances a hypothesis for why signal transduction regulation of barrier function may require these higher supplemental doses to achieve the TJ remodeling and other barrier element changes that are clinically beneficial.

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“…Exposure to divalent xenobiotic metal ions, such as Pb 2+ ( Markovac and Goldstein, 1988 ; Tomsig and Suszkiw, 1995 ; Sun et al, 1999 ; Morales et al, 2011 ) and Cd 2+ ( Beyersmann et al, 1994 ; Morales et al, 2013b ) modulates PKC activity. Specifically, Cd 2+ can exert both activating and inhibitory effects on PKCs ( Block et al, 1992 ; Beyersmann et al, 1994 ; Long, 1997 ) ( Saijoh et al, 1988 ; Speizer et al, 1989 ). Cadmium(II) is a known carcinogen ( Waalkes and Rehm, 1992 ; Jarup et al, 1998 ; Waalkes, 2003 ; Faroon et al, 2012 ) with elevated levels in the environment due to human activity.…”

Section: Introductionmentioning

confidence: 99%

Reactivity of Thiol-Rich Zn Sites in Diacylglycerol-Sensing PKC C1 Domain Probed by NMR Spectroscopy

Cole

Igumenova

2021

Front. Mol. Biosci.

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Conserved homology 1 (C1) domains are peripheral zinc finger domains that are responsible for recruiting their host signaling proteins, including Protein Kinase C (PKC) isoenzymes, to diacylglycerol-containing lipid membranes. In this work, we investigated the reactivity of the C1 structural zinc sites, using the cysteine-rich C1B regulatory region of the PKCα isoform as a paradigm. The choice of Cd2+ as a probe was prompted by previous findings that xenobiotic metal ions modulate PKC activity. Using solution NMR and UV-vis spectroscopy, we found that Cd2+ spontaneously replaced Zn2+ in both structural sites of the C1B domain, with the formation of all-Cd and mixed Zn/Cd protein species. The Cd2+ substitution for Zn2+ preserved the C1B fold and function, as probed by its ability to interact with a potent tumor-promoting agent. Both Cys3His metal-ion sites of C1B have higher affinity to Cd2+ than Zn2+, but are thermodynamically and kinetically inequivalent with respect to the metal ion replacement, despite the identical coordination spheres. We find that even in the presence of the oxygen-rich sites presented by the neighboring peripheral membrane-binding C2 domain, the thiol-rich sites can successfully compete for the available Cd2+. Our results indicate that Cd2+ can target the entire membrane-binding regulatory region of PKCs, and that the competition between the thiol- and oxygen-rich sites will likely determine the activation pattern of PKCs.

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Inhibition of Phorbol Ester Binding and Protein Kinase C Activity by Heavy Metals

Cited by 65 publications

References 9 publications

Molecular Basis for Protein Kinase C Isozyme-Selective Binding: The Synthesis, Folding, and Phorbol Ester Binding of the Cysteine-Rich Domains of All Protein Kinase C Isozymes

Molecular Basis for Protein Kinase C Isozyme-Selective Binding: The Synthesis, Folding, and Phorbol Ester Binding of the Cysteine-Rich Domains of All Protein Kinase C Isozymes

Micronutrients at Supplemental Levels, Tight Junctions and Epithelial Barrier Function: A Narrative Review

Reactivity of Thiol-Rich Zn Sites in Diacylglycerol-Sensing PKC C1 Domain Probed by NMR Spectroscopy

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