A Selective Inhibitor of Cardiac Troponin I Phosphorylation by Delta Protein Kinase C (δPKC) as a Treatment for Ischemia-Reperfusion Injury

Abstract

Myocardial infarction is the leading cause of cardiovascular mortality, with myocardial injury occurring during ischemia and subsequent reperfusion (IR). We previously showed that the inhibition of protein kinase C delta (δPKC) with a pan-inhibitor (δV1-1) mitigates myocardial injury and improves mitochondrial function in animal models of IR, and in humans with acute myocardial infarction, when treated at the time of opening of the occluded blood vessel, at reperfusion. Cardiac troponin I (cTnI), a key sarcomeric protein in cardiomyocyte contraction, is phosphorylated by δPKC during reperfusion. Here, we describe a rationally-designed, selective, high-affinity, eight amino acid peptide that inhibits cTnI’s interaction with, and phosphorylation by, δPKC (ψTnI), and prevents tissue injury in a Langendorff model of myocardial infarction, ex vivo. Unexpectedly, we also found that this treatment attenuates IR-induced mitochondrial dysfunction. These data suggest that δPKC phosphorylation of cTnI is critical in IR injury, and that a cTnI/δPKC interaction inhibitor should be considered as a therapeutic target to reduce cardiac injury after myocardial infarction.

De Novo Development of Mitochondria-Targeted Molecular Probes Targeting Pink1

“…Based on a rational design approach, we developed a selective Pink1 probe. We used an algorithm that identified similar regions in interacting proteins that are otherwise non-related and which was used to generate many effective and selective regulators of protein-protein interactions (PPIs) [ 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 ]. Optic atrophy 1 (Opa1) is a nuclear-encoded mitochondrial protein causing autosomal dominant optic atrophy, and it is a key player in mitochondrial fusion and cristae morphology regulation.…”

Beyond the Low Hanging Fruit: Rationally Designed Peptide as Regulators of Protein-Protein Interactions and Their Applications to Human Disease

“…The peptide demonstrated high binding to the target protein in vitro (KD ∼50 nM), and reduced cardiac injury induced by ischemic events in ex vivo and in vivo animal models (IC50 ∼5 nM) [8]. Based on the same rational, peptides that target the PPI sites of PKCδ and other substrates were developed, including glyceraldehyde-3-phosphate dehydrogenase (GAPDH) [9], myristoylated alanine-rich C-kinase substrate (MARCKS), dynamin-related protein 1 (Drp1), insulin receptor substrate 1 (IRS1) [10], and Troponin I [11]. All these peptides demonstrated high specificity and bioactivity.…”

Extracellular Histone-Induced Protein Kinase C Alpha Activation and Troponin Phosphorylation Is a Potential Mechanism of Cardiac Contractility Depression in Sepsis

“…The role of PKC isoforms in regulating cardiomyocyte contractility has been extensively studied in various scenarios and pathological conditions [ 39 , 49 ]. Although some controversies remain with regard to the direct effects of the different PKC isoforms on cardiac function [ 50 , 51 , 52 ], there are also well-established facts.…”

“…Regulated phosphorylation of troponin I determines troponin positioning for optimal regulation of cardiac muscle contraction [ 37 , 38 ]. Protein kinase A (PKA), protein kinase C (PKC) and their isoforms are the most important kinases related to troponin phosphorylation [ 34 , 35 ] which alter cardiac myofilament properties and ultimately affect inotropy (contraction) and lusitropy (relaxation) of cardiomyocytes [ 34 , 35 , 38 , 39 ]. Abnormally increased cTnI phosphorylation by PKCs has been shown to be detrimental to cardiomyocyte contractility in vitro and in vivo [ 8 , 40 , 41 , 42 , 43 ] with such changes also reported in failing human hearts [ 44 ].…”