入侵病原体与宿主之间呈动态平衡，以维持病原体成功地寄生在宿主体内而不致宿主死亡，这是许多寄生虫感染的一个重要特征。包括曼氏血吸虫在内的许多蠕虫感染中，持续的炎症反应比病原体本身对宿主的危害更大，降低宿主的免疫反应具有重要意义。曼氏血吸虫感染后，宿主活化CD4^＋Th2细胞，分泌IL-4、IL-5和IL-13。最近研究表明IL-13是肝组织纤维化的重要调节因子。

IL-13受体α2降低血吸虫病肉芽肿的炎症反应并延长宿主存活时间[英]/Mentink-Kane MM,Cheever AW，Thompson RW，et al//Proc Natl Acad Sci U S A

WD40 proteins propel cellular networks

The type-1 parathyroid hormone receptor (PTHR1) is a family B G protein–coupled receptor (GPCR) that mediates the actions of two polypeptide ligands; parathyroid hormone (PTH), an endocrine hormone that regulates the levels of calcium and inorganic phosphate in the blood by acting on bone and kidney, and PTH-related protein (PTHrP), a paracrine-factor that regulates cell differentiation and proliferation programs in developing bone and other tissues. The type-2 parathyroid hormone receptor (PTHR2) binds a peptide ligand, called tuberoinfundibular peptide-39 (TIP39), and while the biologic role of the PTHR2/TIP39 system is not as defined as that of the PTHR1, it likely plays a role in the central nervous system as well as in spermatogenesis. Mechanisms of action at these receptors have been explored through a variety of pharmacological and biochemical approaches, and the data obtained support a basic “two-site” mode of ligand binding now thought to be used by each of the family B peptide hormone GPCRs. Recent crystallographic studies on the family B GPCRs are providing new insights that help to further refine the specifics of the overall receptor architecture and modes of ligand docking. One intriguing pharmacological finding for the PTHR1 is that it can form surprisingly stable complexes with certain PTH/PTHrP ligand analogs and thereby mediate markedly prolonged cell signaling responses that persist even when the bulk of the complexes are found in internalized vesicles. The PTHR1 thus appears to be able to activate the Gαs/cAMP pathway not only from the plasma membrane but also from the endosomal domain. The cumulative findings could have an impact on efforts to develop new drug therapies for the PTH receptors.

https://pharmrev.aspetjournals.org/content/pharmrev/67/2/310.full.pdf

International Union of Basic and Clinical Pharmacology. XCIII. The Parathyroid Hormone Receptors—Family B G Protein–Coupled Receptors

Phage display: Concept, innovations, applications and future

Phospholipase C (PLC) converts phosphatidylinositol 4,5-bisphosphate (PIP(2)) to inositol 1,4,5-trisphosphate (IP(3)) and diacylglycerol (DAG). DAG and IP(3) each control diverse cellular processes and are also substrates for synthesis of other important signaling molecules. PLC is thus central to many important interlocking regulatory networks. Mammals express six families of PLCs, each with both unique and overlapping controls over expression and subcellular distribution. Each PLC also responds acutely to its own spectrum of activators that includes heterotrimeric G protein subunits, protein tyrosine kinases, small G proteins, Ca(2+), and phospholipids. Mammalian PLCs are autoinhibited by a region in the catalytic TIM barrel domain that is the target of much of their acute regulation. In combination, the PLCs act as a signaling nexus that integrates numerous signaling inputs, critically governs PIP(2) levels, and regulates production of important second messengers to determine cell behavior over the millisecond to hour timescale.

Mammalian Phospholipase C

G protein betagamma subunits have potential as a target for therapeutic treatment of a number of diseases. We performed virtual docking of a small-molecule library to a site on Gbetagamma subunits that mediates protein interactions. We hypothesized that differential targeting of this surface could allow for selective modulation of Gbetagamma subunit functions. Several compounds bound to Gbetagamma subunits with affinities from 0.1 to 60 muM and selectively modulated functional Gbetagamma-protein-protein interactions in vitro, chemotactic peptide signaling pathways in HL-60 leukocytes, and opioid receptor-dependent analgesia in vivo. These data demonstrate an approach for modulation of G protein-coupled receptor signaling that may represent an important therapeutic strategy.

https://science.sciencemag.org/content/sci/312/5772/443.full.pdf

Differential Targeting of Gßγ-Subunit Signaling with Small Molecules

G protein βγ subunits associate with many binding partners in cellular signaling cascades In previous work, we used random-peptide phage display screening to identify a diverse family of peptides that bound to a common surface on Gβγ subunits and blocked a subset of Gβγ effectors Later studies showed that one of the peptides caused G protein activation through a novel Gβγ-dependent, nucleotide exchange-independent mechanism Here we report the X-ray crystal structure of Gβ1γ2 bound to this peptide, SIGK (SIGKAFKILGYPDYD), at 27 A resolution SIGK forms a helical structure that binds the same face of Gβ1 as the switch II region of Gα The interaction interface can be subdivided into polar and nonpolar interfaces that together contain a mixture of binding determinants that may be responsible for the ability of this surface to recognize multiple protein partners Systematic mutagenic analysis of the peptide−Gβ1 interface indicates that distinct sets of amino acids within this interface are required for bi

Structural and Molecular Characterization of a Preferred Protein Interaction Surface on G Protein βγ Subunits

The G protein-coupled receptor for PTH and PTH-related protein (PTH1R) signals via many intracellular pathways. The purpose of this work is to investigate a G protein binding site on an intracellular domain of the PTH1R. The carboxy-terminal, cytoplasmic tail of the PTH1R fused to glutathione-S-transferase interacts with Gi/o proteins in vitro. All three subunits of the heterotrimer interact with the receptor C-tail. Activation of the heterotrimeric complex with GTPγS has no effect on Gβγ interactions, but markedly disrupts binding of the Gαi/o subunits to the receptor tail, suggesting that direct Gβγ binding indirectly links Gα subunits to this region of the receptor. Gβγ subunits alone bind the C-tail with an affinity that is comparable to the heterotrimeric G protein complex. G protein complexes consisting of Gαshis6-β1γ2 and Gαqhis6-β1γ2 also interact with the PTH1R tail in vitro. The Gβγ interaction domain is located on the juxta-membrane region of the tail between amino acids 468 and 491. Mutations ...

/pdf/a-docking-site-for-g-protein-bg-subunits-on-the-parathyroid-3wvudwegia.pdf

A docking site for G protein βγ subunits on the parathyroid hormone 1 receptor supports signaling through multiple pathways.

Regulatory Interactions between the Amino Terminus of G-protein βγ Subunits and the Catalytic Domain of Phospholipase Cβ2

Peptides derived from a random-peptide phage display screen with purified Gbeta(1)gamma(2) subunits as the target promote the dissociation of G protein heterotrimers in vitro and activate G protein signaling in intact cells. In vitro, one of these peptides (SIRKALNILGYPDYD; SIRK) promotes subunit dissociation by binding directly to Gbetagamma subunits and accelerating the dissociation of GalphaGDP without catalyzing nucleotide exchange. The experiments described here were designed to test whether the mechanism of SIRK action in vitro is in fact the mechanism of action in intact cells. We created a mutant of Gbeta(1) subunits (beta(1)W332A) that does not bind SIRK in vitro. Transfection of Gbeta(1)W332A mutant into Chinese hamster ovary cells blocked peptide-mediated activation of extracellular signal-regulated kinase (ERK), but it did not affect receptor-mediated Gbetagamma subunit-dependent ERK activation, indicating that Gbetagamma subunits are in fact the direct target in cells responsible for ERK activation. To determine whether free Galpha subunits were released from G protein heterotrimers upon peptide treatment, cells were transfected with Ric-8A, a guanine nucleotide exchange factor for free GalphaGDP, but not heterotrimeric G proteins. Ric-8A-transfected cells displayed enhanced myristoyl-SIRKALNILGYPDYD (mSIRK)-dependent inositol phosphate (IP) release and ERK activation. Ric-8A also enhanced ERK activation by the G(i)-linked G protein coupled receptor agonist lysophosphatidic acid. Inhibitors of Gbetagamma subunit function blocked Ric-8-enhanced activation of ERK and IP release. These results suggest that one potential function of Ric-8 in cells is to enhance G protein Gbetagamma subunit signaling. Overall, these experiments provide further support for the hypothesis that mSIRK promotes G protein subunit dissociation to release free betagamma subunits in intact cells.

Tabetha M. Bonacci

Papers

Differential Targeting of Gßγ-Subunit Signaling with Small Molecules

Structural and Molecular Characterization of a Preferred Protein Interaction Surface on G Protein βγ Subunits

A docking site for G protein βγ subunits on the parathyroid hormone 1 receptor supports signaling through multiple pathways.

Regulatory Interactions between the Amino Terminus of G-protein βγ Subunits and the Catalytic Domain of Phospholipase Cβ2

Ric-8 Enhances G Protein βγ-Dependent Signaling in Response to βγ-Binding Peptides in Intact Cells