Proline hydroxylation linked to Akt activation

Precise Identification of Native Peptides with Posttranslational Proline Hydroxylation by Nanopore

Hydroxylation, an extensive post-translational modification on proline, is critical for the modulation of native protein structures, further dominating their functions in life systems. However, current mass spectrometry (MS)-based identification, could hardly distinguish hydroxylation with the neighboring oxidation due to the same mass shifts, as well as challenges posed by low abundance and exogenous oxidation during sample preparation. To address this, an engineered nanopore was designed, capable of discriminating single hydroxyl group on proline, to achieve the identification of proline hydroxylation on individual native peptides directly in mixture. By modeling the interaction between hydroxylated proline and its specific recognition protein, we introduced a hydrophobic region in aerolysin lumen with A224Y/T274W mutations to enhance the sensitivity for proline residue. The results showed that the proline hydroxylation on native HIF-1α fragments could be unambiguously identified without purification, which could be maintained even in the presence of neighboring oxidation. The voltage-dependent experiments further demonstrated the more relaxed peptide structure induced by hydroxylation that supported the great impact of hydroxylation on chemical properties of proline and the molecular mechanism of the specific recognition for hydroxylated proline in nature. These findings highlight the potential of nanopore for precise hydroxylation detection, offering a reliable platform for further uncovering the related functions in biological systems.

AKT kinases as therapeutic targets

AKT, or protein kinase B, is a central node of the PI3K signaling pathway that is pivotal for a range of normal cellular physiologies that also underlie several pathological conditions, including inflammatory and autoimmune diseases, overgrowth syndromes, and neoplastic transformation. These pathologies, notably cancer, arise if either the activity of AKT or its positive or negative upstream or downstream regulators or effectors goes unchecked, superimposed on by its intersection with a slew of other pathways. Targeting the PI3K/AKT pathway is, therefore, a prudent countermeasure. AKT inhibitors have been tested in many clinical trials, primarily in combination with other drugs. While some have recently garnered attention for their favorable profile, concern over resistance and off-target effects have continued to hinder their widespread adoption in the clinic, mandating a discussion on alternative modes of targeting. In this review, we discuss isoform-centric targeting that may be more effective and less toxic than traditional pan-AKT inhibitors and its significance for disease prevention and treatment, including immunotherapy. We also touch on the emerging mutant- or allele-selective covalent allosteric AKT inhibitors (CAAIs), as well as indirect, novel AKT-targeting approaches, and end with a briefing on the ongoing quest for more reliable biomarkers predicting sensitivity and response to AKT inhibitors, and their current state of affairs.

Akt: a key transducer in cancer

Growth factor signaling plays a pivotal role in diverse biological functions, such as cell growth, apoptosis, senescence, and migration and its deregulation has been linked to various human diseases. Akt kinase is a central player transmitting extracellular clues to various cellular compartments, in turn executing these biological processes. Since the discovery of Akt three decades ago, the tremendous progress towards identifying its upstream regulators and downstream effectors and its roles in cancer has been made, offering novel paradigms and therapeutic strategies for targeting human diseases and cancers with deregulated Akt activation. Unraveling the molecular mechanisms for Akt signaling networks paves the way for developing selective inhibitors targeting Akt and its signaling regulation for the management of human diseases including cancer.

Hydroxyproline in animal metabolism, nutrition, and cell signaling

trans-4-Hydroxy-L-proline is highly abundant in collagen (accounting for about one-third of body proteins in humans and other animals). This imino acid (loosely called amino acid) and its minor analogue trans-3-hydroxy-L-proline in their ratio of approximately 100:1 are formed from the post-translational hydroxylation of proteins (primarily collagen and, to a much lesser extent, non-collagen proteins). Besides their structural and physiological significance in the connective tissue, both trans-4-hydroxy-L-proline and trans-3-hydroxy-L-proline can scavenge reactive oxygen species and have both structural and physiological significance in animals. The formation of trans-4-hydroxy-L-proline residues in protein kinases B and DYRK1A, eukaryotic elongation factor 2 activity, and hypoxia-inducible transcription factor plays an important role in regulating their phosphorylation and catalytic activation as well as cell signaling in animal cells. These biochemical events contribute to the modulation of cell metabolism, growth, development, responses to nutritional and physiological changes (e.g., dietary protein intake and hypoxia), and survival. Milk, meat, skin hydrolysates, and blood, as well as whole-body collagen degradation provide a large amount of trans-4-hydroxy-L-proline. In animals, most (nearly 90%) of the collagen-derived trans-4-hydroxy-L-proline is catabolized to glycine via the trans-4-hydroxy-L-proline oxidase pathway, and trans-3-hydroxy-L-proline is degraded via the trans-3-hydroxy-L-proline dehydratase pathway to ornithine and glutamate, thereby conserving dietary and endogenously synthesized proline and arginine. Supplementing trans-4-hydroxy-L-proline or its small peptides to plant-based diets can alleviate oxidative stress, while increasing collagen synthesis and accretion in the body. New knowledge of hydroxyproline biochemistry and nutrition aids in improving the growth, health and well-being of humans and other animals.

Effects of compound deer bone extract on osteoporosis model mice and intestinal microflora

The preventive and therapeutic mechanisms of CDBE on osteoporosis were studied by observing the serum bone-related biochemical indicators, bone trabecular micro-structure and intestinal flora in ovariectomized osteoporosis model mice, in order to provide a scientific theoretical basis for the further study on the effect of CDBE on osteoporosis, and the prevention and treatment of osteoporosis with clinical traditional Chinese medicines. The components in CDBE were detected by UHPLC-MS. A mouse osteoporosis model was established by the bilateral ovariectomy in female ICR mice. The biochemical indicators related to osteoporosis were detected, the right proximal tibia was scanned by Micro-CT, the intestinal microflora in the colon contents were examined, and the changes of microflora were taken as the main target to evaluate the effect of CDBE on the intestinal microflora in the model mice. A total of 16 compounds were obtained by the combined application of UHPLC-MS. CDBE could significantly increase the contents of E2, Ca²⁺ , CT, HyP, OCN, FOXP3, P1NP and CTX-II, in the model mice. CDBE could significantly improve the trabecular micro-structure, Tb.N, Tb.Sp, SMI and Conn.D. CDBE could make the intestinal flora of osteoporosis model mice tend to healthy mice in species and quantity. CDBE can improve the symptoms of postmenopausal osteoporosis in mice, with a positive effect on the intestinal flora of postmenopausal mice. Its mechanism of regulating the symptoms of osteoporosis may be related to the regulation of bone-related biochemical indicators in the serum of mice. PRACTICAL APPLICATIONS: This research has a positive impact on the development of functional food with anti-osteoporosis in the future.