Lower troponin expression in the right ventricle of rats explains interventricular differences in E-C coupling

Unique responses of the fixed stoichiometric TRPC1-TRPC5 concatemer to G proteins

Transient receptor potential canonical (TRPC)5 channel is a non-selective cation channel that plays a significant role in membrane depolarization and calcium influx. TRPC5 not only forms homotetramers itself but also heterotetramers with TRPC1. However, accurately testing and confirming these heterotetrameric channels at specific ratios has proven challenging. Therefore, creating heteromeric concatemers of TRPC5 and TRPC1 with a fixed stoichiometry of 1:1 becomes essential. This study aims to meticulously identify and reaffirm the properties of TRPC5 homomers and heteromers with a 1:1 fixed stoichiometry to determine the optimal ratio for the TRPC1/5 heterotetramer. The overall characteristics were consistent with those of the previous studies, but several specific features were different. The TRPC1-TRPC5 concatemer is activated by Englerin A and GiQL, whereas carbachol alone does not trigger its activation. Additionally, GqQL significantly inhibited the current when co-expressed with the concatemer. Interestingly, carbachol can activate the TRPC1-TRPC5 concatemer in the presence of internal GTPγS, highlighting the influence of intracellular signaling conditions on its activation. Meanwhile, the TRPC5-TRPC5 concatemer is responsive to both carbachol and Englerin A. In conclusion, we provide evidence that the TRPC1-TRPC5 heteromeric concatemer with fixed stoichiometry need specific conditions to respond to carbachol, whereas the TRPC5-TRPC5 homomeric concatemer responds physiologically to carbachol. Additional research may be necessary to ascertain the optimal stoichiometry for the TRPC1-TRPC5 concatemer to enhance its electrophysiological properties.

Covalent conjugation with quercetin mitigates allergenicity of the bee pollen allergen Bra c p in a murine model

Profilin family members are highly conserved food allergens that can cause widespread cross-allergic reactions. Our previous research has demonstrated that the covalent conjunction with quercetin can disrupt the conformational epitopes of a profilin allergen, Bra c p. In this study, we further investigated the intrinsic molecular mechanisms using molecular dynamics simulations. Moreover, the allergenic potential of Bra c p and its conjugate with quercetin was assessed in BALB/c mice. The results showed that continuous interaction with quercetin increased the molecular motion of Bra c p, causing changes to its α-helices and exposing hydrophobic residues which altered antigenic epitopes. Additionally, mice treated with Bra c p-quercetin conjugate showed reduced allergic reactions compared to those treated with Bra c p alone by regulating purine metabolism, calcium signaling, and CD4+CD25+ Tregs proportion. Quercetin conjugation decreases the allergenicity of Bra c p, providing a scientific foundation for reducing the profilin allergens in food.

Physiology of intracellular calcium buffering

Calcium signaling underlies much of physiology. Almost all the Ca2+ in the cytoplasm is bound to buffers, with typically only ∼1% being freely ionized at resting levels in most cells. Physiological Ca2+ buffers include small molecules and proteins, and experimentally Ca2+ indicators will also buffer calcium. The chemistry of interactions between Ca2+ and buffers determines the extent and speed of Ca2+ binding. The physiological effects of Ca2+ buffers are determined by the kinetics with which they bind Ca2+ and their mobility within the cell. The degree of buffering depends on factors such as the affinity for Ca2+, the Ca2+ concentration, and whether Ca2+ ions bind cooperatively. Buffering affects both the amplitude and time course of cytoplasmic Ca2+ signals as well as changes of Ca2+ concentration in organelles. It can also facilitate Ca2+ diffusion inside the cell. Ca2+ buffering affects synaptic transmission, muscle contraction, Ca2+ transport across epithelia, and the killing of bacteria. Saturation of buffers leads to synaptic facilitation and tetanic contraction in skeletal muscle and may play a role in inotropy in the heart. This review focuses on the link between buffer chemistry and function and how Ca2+ buffering affects normal physiology and the consequences of changes in disease. As well as summarizing what is known, we point out the many areas where further work is required.

Troponin levels make a difference

JGP study reveals that lower troponin expression in the right ventricle underlies interventricular differences in excitation-contraction coupling.