Tyrosinase-Catalyzed Peptide Macrocyclization for mRNA Display

mRNA display of macrocyclic peptides has proven itself to be a powerful technique to discover high-affinity ligands for a protein target. However, only a limited number of cyclization chemistries are known to be compatible with mRNA display. Tyrosinase is a copper-dependent oxidase that oxidizes tyrosine phenol to an electrophilic o-quinone, which is readily attacked by cysteine thiol. Here we show that peptides containing tyrosine and cysteine are rapidly cyclized upon tyrosinase treatment. Characterization of the cyclization reveals it to be widely applicable to multiple macrocycle sizes and scaffolds. We combine tyrosinase-mediated cyclization with mRNA display to discover new macrocyclic ligands targeting melanoma-associated antigen A4 (MAGE-A4). These macrocycles potently inhibit the MAGE-A4 binding axis with nanomolar IC50 values. Importantly, macrocyclic ligands show clear advantage over noncyclized analogues with ∼40-fold or greater decrease in IC50 values.

Discovery and Structural Basis of the Selectivity of Potent Cyclic Peptide Inhibitors of MAGE-A4

MAGE proteins are cancer testis antigens (CTAs) that are characterized by highly conserved MAGE homology domains (MHDs) and are increasingly being found to play pivotal roles in promoting aggressive cancer types. MAGE-A4, in particular, increases DNA damage tolerance and chemoresistance in a variety of cancers by stabilizing the E3-ligase RAD18 and promoting trans-lesion synthesis (TLS). Inhibition of the MAGE-A4:RAD18 axis could sensitize cancer cells to chemotherapeutics like platinating agents. We use an mRNA display of thioether cyclized peptides to identify a series of potent and highly selective macrocyclic inhibitors of the MAGE-A4:RAD18 interaction. Co-crystal structure indicates that these inhibitors bind in a pocket that is conserved across MHDs but take advantage of A4-specific residues to achieve high isoform selectivity. Cumulatively, our data represent the first reported inhibitor of the MAGE-A4:RAD18 interaction and establish biochemical tools and structural insights for the future development of MAGE-A4-targeted cellular probes.

An Integrated Risk Reduction Intervention can reduce body mass index in individuals being treated for bipolar I disorder: results from a randomized trial

OBJECTIVES

We conducted a randomized, controlled trial comparing the efficacy of an Integrated Risk Reduction Intervention (IRRI) to a control condition with the objective of improving mood stability and psychosocial functioning by reducing cardiometabolic risk factors in overweight/obese patients with bipolar I disorder.

METHODS

A total of 122 patients were recruited from our outpatient services and randomly allocated to IRRI (n = 61) or psychiatric care with medical monitoring (n = 61). Individuals allocated to IRRI received psychiatric treatment and assessment, medical monitoring by a nurse, and a healthy lifestyle program from a lifestyle coach. Those allocated to the control condition received psychiatric treatment and assessment and referral, if indicated, for medical problems. A mixed-effects model was used to examine the impact of the interventions on body mass index (BMI). Exploratory moderator analyses were used to characterize those individuals likely to benefit from each treatment approach.

RESULTS

Analyses were conducted on data for the IRRI (n = 58) and control (n = 56) participants with ≥ 1 study visit. IRRI was associated with a significantly greater rate of decrease in BMI (d = -0.51, 95% confidence interval: -0.91 to -0.14). Three variables (C-reactive protein, total cholesterol, and instability of total sleep time) contributed to a combined moderator of faster decrease in BMI with IRRI treatment.

CONCLUSIONS

Overweight/obese patients with bipolar disorder can make modest improvements in BMI, even when taking medications with known potential for weight gain. Our finding that a combination of three baseline variables provides a profile of patients likely to benefit from IRRI will need to be tested further to evaluate its utility in clinical practice.

Antigen receptors on immature, but not mature, B and T cells are coupled to cytosolic phospholipase A2 activation: expression and activation of cytosolic phospholipase A2 correlate with lymphocyte maturation

The Ag receptors on mature B and T cells are not coupled to the activation of cytosolic phospholipase A2 (cPLA2) and arachidonic acid release. Moreover, phorbol esters such as PMA, which can activate cPLA2 via mitogen-activated protein (MAP) kinase in most cell types, also failed to induce the release of arachidonate from mature cells, suggesting that the cPLA2 pathway may not be functional in mature lymphocytes. Interestingly, Western blot analysis revealed that cPLA2, which had previously been thought to be expressed ubiquitously, is not expressed in mature B or T cells and that cytosolic phospholipase A2 expression could not be up-regulated in lymphocytes following culture with a range of cytokines most likely to be involved in an immune response such as IL-1 alpha, IL-3, or TNF-alpha. In contrast, cPLA2 was shown to be expressed and activated in thymocytes and immature B cells under conditions in which ligation of the Ag receptors led to growth arrest and/or apoptosis. Taken together, these data suggest that cPLA2 does not play a role in Ag receptor-mediated lymphocyte activation, but may be involved in the molecular mechanisms underlying lymphocyte maturation and/or self tolerance by clonal deletion.

Antigen receptors on immature, but not mature, B and T cells are coupled to cytosolic phospholipase A2 activation: expression and activation of cytosolic phospholipase A2 correlate with lymphocyte maturation

The Ag receptors on mature B and T cells are not coupled to the activation of cytosolic phospholipase A2 (cPLA2) and arachidonic acid release. Moreover, phorbol esters such as PMA, which can activate cPLA2 via mitogen-activated protein (MAP) kinase in most cell types, also failed to induce the release of arachidonate from mature cells, suggesting that the cPLA2 pathway may not be functional in mature lymphocytes. Interestingly, Western blot analysis revealed that cPLA2, which had previously been thought to be expressed ubiquitously, is not expressed in mature B or T cells and that cytosolic phospholipase A2 expression could not be up-regulated in lymphocytes following culture with a range of cytokines most likely to be involved in an immune response such as IL-1 alpha, IL-3, or TNF-alpha. In contrast, cPLA2 was shown to be expressed and activated in thymocytes and immature B cells under conditions in which ligation of the Ag receptors led to growth arrest and/or apoptosis. Taken together, these data suggest that cPLA2 does not play a role in Ag receptor-mediated lymphocyte activation, but may be involved in the molecular mechanisms underlying lymphocyte maturation and/or self tolerance by clonal deletion.

Reversible cerebral segmental vasoconstriction

Vasoconstriction is not recognized as a cause of cerebrovascular disease except in the vasospasm seen following subarachnoid hemorrhage and possibly in migraine. However, we found four patients to have transient, fully reversible vasoconstriction and dilatation prominently involving arteries around the circle of Willis. All four patients were evaluated for severe headaches and fluctuating or recurring motor or sensory deficits. No cause for the clinical syndromes and angiographic abnormalities was found. Similar patients are reported in the literature under various nosologies. This newly recognized clinical-angiographic syndrome should be differentiated from other known causes of vessel constriction and dilatation; the precipitants of reversible vasoconstriction may then be better defined.

Multiple sclerosis: decreased relapse rate through dietary supplementation with calcium, magnesium and vitamin D

A group of young patients having multiple sclerosis was treated with dietary supplements containing calcium, magnesium and vitamin D for a period of one to two years. The experimental design employed self-pairing: the response of each patient was compared with his/her own case history as control. The number of exacerbations observed during the program was less than one half the number expected from case histories. No side effects were apparent. The dietary regimen may offer a new means of controlling the exacerbation rate in MS, at least for younger patients. The results tend to support a theory of MS which states that calcium and magnesium are important in the development, structure and stability of myelin.