Binding of smoothelin-like 1 to tropomyosin and calmodulin is mutually exclusive and regulated by phosphorylation

Smoothelin-like 1 knockout mice display sex-dependent alterations in blood flow and cardiac function

Smoothelin-like 1 (SMTNL1) modulates the contractile performance of smooth muscle and thus has a key role in vascular homeostasis. Elevated vascular tone, recognized as a contributor to the development of progressive cardiac dysfunction, was previously found with SMTNL1 deletion. In this study, we assessed cardiac morphology and function of male and female, wild-type (Smtnl1^+/+) and global SMTNL1 knockout (Smtnl1^-/-) mice at 10 weeks of age. Gross dissection revealed distinct cardiac morphology only in males; Smtnl1^-/- hearts were significantly smaller than Smtnl1^+/+, but the left ventricle (LV) proportion of heart mass was greater. Male Smtnl1^-/- mice also displayed increased ejection fraction and fractional shortening, as well as elevated aortic and pulmonary flow velocities. The impact of cardiac stress with pressure overload by transverse aortic constriction (TAC) was examined in male mice. With TAC banding, systolic function was preserved, but the LV filling pressure was selectively elevated due to relaxation impairment. Smtnl1^-/- mice displayed higher early/passive filling velocity of LV/early mitral annulus velocity ratio (E/E' ratio) and myocardial performance index along with a prolonged isovolumetric relaxation time. Taken together, the findings support a novel, sex-dimorphic role for SMTNL1 in modulating cardiac structure and function of mice.

Retene, pyrene and phenanthrene cause distinct molecular-level changes in the cardiac tissue of rainbow trout (Oncorhynchus mykiss) larvae, part 2 - Proteomics and metabolomics

Polycyclic aromatic hydrocarbons (PAHs) are global contaminants of concern. Despite several decades of research, their mechanisms of toxicity are not very well understood. Early life stages of fish are particularly sensitive with the developing cardiac tissue being a main target of PAHs toxicity. The mechanisms of cardiotoxicity of the three widespread model polycyclic aromatic hydrocarbons (PAHs) retene, pyrene and phenanthrene were explored in rainbow trout (Oncorhynchus mykiss) early life stages. Newly hatched larvae were exposed to sublethal doses of each individual PAH causing no detectable morphometric alterations. Changes in the cardiac proteome and metabolome were assessed after 7 or 14 days of exposure to each PAH. Phase I and II enzymes regulated by the aryl hydrocarbon receptor were significantly induced by all PAHs, with retene being the most potent compound. Retene significantly altered the level of several proteins involved in key cardiac functions such as muscle contraction, cellular tight junctions or calcium homeostasis. Those findings were quite consistent with previous reports regarding the effects of retene on the cardiac transcriptome. Significant changes in proteins linked to iron and heme metabolism were observed following exposure to pyrene. While phenanthrene also altered the levels of several proteins in the cardiac tissue, no clear mechanisms or pathways could be highlighted. Due to high variability between samples, very few significant changes were detected in the cardiac metabolome overall. Slight but significant changes were still observed for pyrene and phenanthrene, suggesting possible effects on several energetic or signaling pathways. This study shows that early exposure to different PAHs can alter the expression of key proteins involved in the cardiac function, which could potentially affect negatively the fitness of the larvae and later of the juvenile fish.

Structural Characteristics, Binding Partners and Related Diseases of the Calponin Homology (CH) Domain

The calponin homology (CH) domain is one of the most common modules in various actin-binding proteins and is characterized by an α-helical fold. The CH domain plays important regulatory roles in both cytoskeletal dynamics and signaling. The CH domain is required for stability and organization of the actin cytoskeleton, calcium mobilization and activation of downstream pathways. The CH domain has recently garnered increased attention due to its importance in the onset of different diseases, such as cancers and asthma. However, many roles of the CH domain in various protein functions and corresponding diseases are still unclear. Here, we review current knowledge about the structural features, interactome and related diseases of the CH domain.