Pin1 is a human protein classified as a peptidyl-prolyl cis/trans isomerase. The protein regulates the conformation of phosphorylated protein substrates by rotating the peptide bond between phosphorylated serine/threonine residues that precede proline residues. Structurally, Pin1 consists of an N-terminal WW domain and a C-terminal PPIase domain. The PPIase domain catalyzes cis/trans isomerization of peptide bonds in substrate proteins that contain the aforementioned consensus motif. We hypothesize that Pin1 binding is positively impacted when two phospho-acceptor sites on peptides derived from mitotic phosphatase CDC25C, a known Pin1-interacting protein, are phosphorylated. Using nuclear magnetic resonance and fluorescence polarization, binding affinities of CDC25C peptides to Pin1 were calculated. The results indicate that doubly-phosphorylated peptides bound to Pin1 have lower dissociation constants and consequently greater binding affinities, than complexes containing non- or singly-phosphorylated peptides, at the equivalent residues. This suggests that Pin1 has two independent phospho-binding sites that when bound, increase substrate binding affinity.

The enzyme Pin1 is a peptidyl-prolyl cis-trans isomerase consisting structurally of two domains, an N-terminal WW protein interaction domain and a C-terminal PPIase catalytic domain. Both domains bind a phosphorylated serine/threonine-proline motif, however, a precise mechanism regarding how binding to interactors is coordinated by both domains has not yet been determined. Although multiple models exist to explain this process, it appears that the interactions may be substrate-specific. With regards to a well-studied Pin1 interactor, CDC25C, we hypothesize that binding occurs via the simultaneous model. This model suggests that two binding sites, each having low affinity, may bind in concert producing a higher affinity interaction. To investigate this we chose to employ a peptide-based approach, using human CDC25C-derived peptides which contained the two identified Pin1 binding sites in phosphorylated and non-phosphorylated combinations. These peptides were utilized in two independent assays, surface plasmon resonance and fluorescence polarization, to elucidate the domain- and phosphorylation-requirements of the Pin1-CDC 25C interaction. We showed that the interaction is phosphorylation-dependent, and is optimal when full- length, wild-type Pin1 binds to a doubly-phosphorylated peptide. Collectively, our results support our hypothesis that the Pin1-CDC25C interaction occurs via the simultaneous model, and requires both domains.

Pin1 is an essential peptidyl-prolyl isomerase (PPIase) that catalyzes cis-trans prolyl isomerization in proteins containing phosphorylated serine/threonine-proline motifs (pSer/Thr-Pro). It has an N-terminal binding domain (WW) and a C-terminal PPIase domain. Pin1 targets pSer/Thr-Pro motifs by its WW domain and catalyzes isomerization through its PPIase domain. This dissertation is focused on elucidating the interactions between Pin1/substrate, the inter-domain dynamics upon binding, and the catalytic activity of Pin1 upon binding different substrates. Specifically, we investigated the Pin1-Histone H1 interaction and designed a series of chimeric peptides based on the H1.4 sequence (KATGAApTPKKSAKW). NMR titrations were performed for each peptide using both full-length Pin1 as well as the WW domain alone, to analyze the binding affinities. Here we combined 15N relaxation and residual dipolar couplings (RDCs) to monitor the degree to which peptide binding induced inter-domain interactions. We also investigated whether our chimeric sequences could alter catalysis (kex) using 1H-1H EXSY NMR experiments. Finally, when combined with molecular modeling, our results suggest a structural basis for how substrate binding can alter Pin1 inter-domain dynamics..

15 chapters on protein phosphorylation and human health written by expert scientists. Covers most important research hot points, such as Akt, AMPK and mTOR. Bridges the basic protein phosphorylation pathways with human health and diseases. Detailed and comprehensive text with excellent figure illustration.

The volumes in this authoritative series present a multidisciplinary approach to modeling and simulation of flows in the cardiovascular and ventilatory systems, especially multiscale modeling and coupled simulations. The cardiovascular and respiratory systems are tightly coupled, as their primary function is to supply oxygen to and remove carbon dioxide from the body's cells. Because physiological conduits have deformable and reactive walls, macroscopic flow behavior and prediction must be coupled to phenomenological models of nano- and microscopic events in a corrector scheme of regulated mechanisms when the vessel lumen caliber varies markedly. Therefore, investigation of flows of blood and air in physiological conduits requires an understanding of the biology, chemistry, and physics of these systems together with the mathematical tools to describe their functioning. Volume 4 is devoted to major sets of intracellular mediators that transmit signals upon stimulation of cell-surface receptors. Activation of signaling effectors triggers the release of substances stored in cellular organelles and/or gene transcription and protein synthesis. Complex stages of cell signaling can be studied using proper mathematical models, once the role of each component is carefully handled. Volume 4 also reviews various categories of cytosolic and/or nuclear mediators and illustrates some major signal transduction pathways, such as NFkappaB axis, oxygen sensing, and mechanotransduction.

Cyclin Dependent Kinase 5 provides a comprehensive and up-to-date collection of reviews on the discovery, signaling mechanisms and functions of Cdk5, as well as the potential implication of Cdk5 in the treatment of neurodegenerative diseases. Since the identification of this unique member of the Cdk family, Cdk5 has emerged as one of the most important signal transduction mediators in the development, maintenance and fine-tuning of neuronal functions and networking. Further studies have revealed that Cdk5 is also associated with the regulation of neuronal survival during both developmental stages and in neurodegenerative diseases. These observations indicate that precise control of Cdk5 is essential for the regulation of neuronal survival. The pivotal role Cdk5 appears to play in both the regulation of neuronal survival and synaptic functions thus raises the interesting possibility that Cdk5 inhibitors may serve as therapeutic treatment for a number of neurodegenerative diseases.