Cardiac physiology and pathology have been extensively explored at the transcriptional level. Still, they are less understood at the translational level, including three major knowledge gaps: pathophysiological impact, molecular mechanisms, and therapeutic implications of translational control in cardiac biology and heart disease. This review aims to provide a summary of the most recent key findings in this emerging field of translational control in heart health and disease, covering the physiological functions, disease pathogenesis, biochemical mechanisms, and development of potential RNA-based, translation-manipulating drugs. Translation of mRNA to protein is the final step in the central dogma for protein synthesis. Translation machinery includes a family of essential “housekeeping” factors and enzymes required for mRNA translation. These translation factors ensure the accurate processing of mRNA to protein according to the genetic code and maintain the optimal quality and quantity of cellular proteins for normal cardiac function. Translation factors also regulate the efficiency, speed, and fidelity of protein production and play a role in cardiac pathological remodeling under stress conditions. This review first introduces the techniques and methods used to study the translational regulation of gene expression in the cardiac system. We then summarize discoveries of a variety of pathophysiological functions and molecular mechanisms of translational control in cardiac health and disease, focusing on two primary symptoms, cardiac hypertrophy and fibrosis. In these sessions, we discuss the translational regulation directed by specific regulatory factors in cardiac physiology and how their genetic mutations, expression dysregulation, or functional alterations contribute to the etiology of heart disease. Notably, translational control exhibits extensive crosstalk with other processes, including transcriptional regulation, mitochondrial metabolism, and sarcomere homeostasis. Furthermore, recent findings have revealed the role of translational regulation in cardiomyocyte proliferation and heart regeneration, providing new approaches for creating regenerative medicine. Because transcript-specific translational regulation of both pathological and protective proteins occurs in heart disease, target-selective translation inhibitors and enhancers can be developed. These inhibitors and enhancers offer valuable insights into novel therapeutic targets and the development of RNA-based drugs for heart disease treatment.

Cdc14 phosphatases are related structurally and mechanistically to protein tyrosine phosphatases (PTPs) but evolved a unique specificity for phosphoSer-Pro-X-Lys/Arg sites primarily deposited by cyclin-dependent kinases. This specialization is widely conserved in eukaryotes. The evolutionary reconfiguration of the Cdc14 active site to selectively accommodate phosphoSer-Pro likely required modification to the canonical PTP catalytic cycle. While studying Saccharomyces cerevisiae Cdc14, we discovered a short sequence in the disordered C terminus, distal to the catalytic domain, which mimics an optimal substrate. Kinetic analyses demonstrated this pseudosubstrate binds the active site and strongly stimulates rate-limiting phosphoenzyme hydrolysis, and we named it "substrate-like catalytic enhancer" (SLiCE). The SLiCE motif is found in all Dikarya fungal Cdc14 orthologs and contains an invariant glutamine, which we propose is positioned via substrate-like contacts to assist orientation of the hydrolytic water, similar to a conserved active site glutamine in other PTPs that Cdc14 lacks. AlphaFold2 predictions revealed vertebrate Cdc14 orthologs contain a conserved C-terminal alpha helix bound to the active site. Although apparently unrelated to the fungal sequence, this motif also makes substratelike contacts and has an invariant glutamine in the catalytic pocket. Altering these residues in human Cdc14A and Cdc14B demonstrated that it functions by the same mechanism as the fungal motif. However, the fungal and vertebrate SLiCE motifs were not functionally interchangeable, illuminating potential active site differences during catalysis. Finally, we show that the fungal SLiCE motif is a target for phosphoregulation of Cdc14 activity. Our study uncovered evolution of an unusual stimulatory pseudosubstrate motif in Cdc14 phosphatases.

Cardiac physiology and pathology have been extensively explored at the transcriptional level, but are less understood at the translational level. Translation of mRNA to protein is the final step in the central dogma for protein synthesis. Translation machinery includes a family of essential “housekeeping” factors and enzymes required for mRNA translation. These translation factors ensure the accurate processing of mRNA to protein according to the genetic code and maintain the optimal quality and quantity of cellular proteins for normal cardiac function. Translation factors also control the efficiency, speed, and fidelity of protein production and participate in cardiac pathological remodeling under stress conditions. This review summarizes discoveries of the pathophysiological function and molecular mechanism of translational control in cardiac health and disease. Translational control has extensive crosstalk to other processes such as transcriptional regulation, mi-tochondrial metabolism, and sarcomere homeostasis. We discuss the translational regu-lation directed by specific regulatory factors in cardiac physiology and the etiology of heart disease when they undergo genetic mutation, expression dysregulation, or func-tional alteration. Because transcript-specific translational regulation of pathological and protective proteins occurs in heart disease, target-selective translation inhibitors and enhancers can be developed. These inhibitors and enhancers provide valuable insights into novel therapeutic targets and RNA-based drug development for heart disease treatment.

Background Previous studies of drugs targeting mixed linage kinase type 3 (MLK3) and/or leucine rich repeat kinase type 2 (LRRK2) in sporadic Parkinsons disease (PD) have failed to meet clinical endpoints despite multiple lines of evidence implicating these kinases in pathogenesis. This has reduced enthusiasm for MLK3 and LRRK2 as druggable targets. Largely overlooked is the evidence that these targets remain valid but must be considered in combination to achieve a therapeutic outcome. This provides the rationale for this study. Methods We conducted a pilot study modeling early, pre-symptomatic PD with subsequent evaluation of therapeutic potential of a multi-kinase inhibitor (URMC-099) in alleviating disease pathology. Sprague Dawley rats received unilateral intranigral injections of low dose AAV-haSyn. After a two-week recovery period, all animals were administered either once-daily intraperitoneal (i.p.) injection of URMC-099 or its vehicle control until their terminal endpoint. Induction of early PD, and its alleviation with URMC-099, was evaluated by lateralized motor impairment using the cylinder test and immunohistochemical analysis of neuropathology in the substantia nigra (SN) and striatum. Finally, an in vitro microglial PD model exposed to aSyn pre-formed fibrils and treated with URMC-099 was used to further evaluate the mechanism underlying therapeutic activity. Results A unilateral model of early and progressive AAV-haSyn model for PD was used to demonstrate the therapeutic potential of a targeted multi-kinase inhibitor to attenuate PD-associated neuropathology and prevent the manifestation of lateral motor deficits. Immunohistochemical analysis revealed protection of neuronal cellular integrity along the nigral-striatal pathway with once-daily i.p. URMC-099. The mitigation of degenerative neuropathology was linked to targeted inhibition of MLK3 and LRRK2 and complemented by reduced levels of gliosis in astrocytes and microglia in the SN. Single-microglia segmentation analysis suggested URMC-099 treatment preserved dynamic effector state switching in microglia to enhance autophagic flux to reduce the overall burden of pathologic aSyn. Transcriptomic analysis of a complementary in vitro microglia model corroborated the retention of a homeostatic-like effector state with URMC-099 treatment that was unique to MLK3/LRRK2 dual inhibition. Conclusions Unilateral injection of low dose AAV-haSyn successfully resulted in a lateralized model of early, progressive PD. Dual inhibition of aberrant MLK3 and LRRK2 activity with once-daily i.p. URMC-099 therapy significantly mitigated the development of PD pathology and progression in an early manifest phenotype. Our results present a potential mechanism of therapeutic action dependent on the dual inhibition of MLK3 and LRRK2. This presents a novel therapeutic modality that may be beneficial to a broad population of etiologic PD patients.