Honors & Awards

  • Diabetes Knowledge Award, Stanford Diabetes Research Center (2019)
  • Pre-doctoral fellowship, Stanford Bio-X and Stanford Interdisciplinary Graduate Fellowship (SIGF) (2017)
  • Centennial Teaching Award, Stanford University - Office of the Vice Provost for Teaching and Learning (2016)
  • Program trainee, Stanford ChEM-H - Pre-doctoral Training Program at the Chemistry-Biology Interface (2015)

Education & Certifications

  • B.S., Ouachita Baptist University, Arkadelphia, Arkansas, Majors in Professional Chemistry and Physics, Minors in Mathematics and Biology (2014)

Stanford Advisors

Lab Affiliations

All Publications

  • PAM staining intensity of primary neuroendocrine neoplasms is a potential prognostic biomarker. Scientific reports Horton, T. M., Sundaram, V., Lee, C. H., Hornbacker, K., Van Vleck, A., Benjamin, K. N., Zemek, A., Longacre, T. A., Kunz, P. L., Annes, J. P. 2020; 10 (1): 10943


    Neuroendocrine neoplasms (NENs) are rare epithelial tumors with heterogeneous and frequently unpredictable clinical behavior. Available biomarkers are insufficient to guide individual patient prognosis or therapy selection. Peptidylglycine α-amidating monooxygenase (PAM) is an enzyme expressed by neuroendocrine cells that participates in hormone maturation. The objective of this study was to assess the distribution, clinical associations and survival implications of PAM immunoreactivity in primary NENs. Of 109 primary NENs, 7% were PAM-negative, 25% were PAM-low and 68% were PAM-high. Staining intensity was high in small bowel (p = 0.04) and low in stomach (p = 0.004) NENs. PAM staining was lower in higher grade tumors (p < 0.001) and patients who died (p < 0.001) but did not vary by tumor size or stage at surgery. In patients who died, time to death was shorter in patients with reduced PAM immunoreactivity: median times to death were 11.3 (PAM-negative), 29.4 (PAM-low) and 61.7 (PAM-high) months. Lower PAM staining was associated with increased risk of death after adjusting for disease stage [PAM negative, HR = 13.8 (CI: 4.2-45.5)]. PAM immunoreactivity in primary NENs is readily assessable and a potentially useful stage-independent predictor of survival.

    View details for DOI 10.1038/s41598-020-68071-6

    View details for PubMedID 32616904

  • Generation of highly potent DYRK1A-dependent inducers of human beta-Cell replication via Multi-Dimensional compound optimization. Bioorganic & medicinal chemistry Allegretti, P. A., Horton, T. M., Abdolazimi, Y., Moeller, H. P., Yeh, B., Caffet, M., Michel, G., Smith, M., Annes, J. P. 2019: 115193


    Small molecule stimulation of beta-cell regeneration has emerged as a promising therapeutic strategy for diabetes. Although chemical inhibition of dual specificity tyrosine-phosphorylation-regulated kinase 1A (DYRK1A) is sufficient to enhance beta-cell replication, current lead compounds have inadequate cellular potency for in vivo application. Herein, we report the clinical stage anti-cancer kinase inhibitor OTS167 as a structurally novel, remarkably potent DYRK1A inhibitor and inducer of human beta-cell replication. Unfortunately, OTS167's target promiscuity and cytotoxicity curtails utility. To tailor kinase selectivity towards DYRK1A and reduce cytotoxicity we designed a library of fifty-one OTS167 derivatives based upon a modeled structure of the DYRK1A-OTS167 complex. Indeed, derivative characterization yielded several leads with exceptional DYRK1A inhibition and human beta-cell replication promoting potencies but substantially reduced cytotoxicity. These compounds are the most potent human beta-cell replication-promoting compounds yet described and exemplify the potential to purposefully leverage off-target activities of advanced stage compounds for a desired application.

    View details for DOI 10.1016/j.bmc.2019.115193

    View details for PubMedID 31757680

  • Structure of the IFN gamma receptor complex guides design of biased agonists NATURE Mendoza, J. L., Escalante, N. K., Jude, K. M., Bellon, J., Su, L., Horton, T. M., Tsutsumi, N., Berardinelli, S. J., Haltiwanger, R. S., Piehler, J., Engleman, E. G., Garcia, K. 2019; 567 (7746): 56-+
  • CC-401 Promotes β-Cell Replication via Pleiotropic Consequences of DYRK1A/B Inhibition. Endocrinology Abdolazimi, Y., Lee, S., Xu, H., Allegretti, P., Horton, T. M., Yeh, B., Moeller, H. P., Nichols, R. J., McCutcheon, D., Shalizi, A., Smith, M., Armstrong, N. A., Annes, J. P. 2018


    Pharmacologic expansion of endogenous β-cells is a promising therapeutic strategy for diabetes. To elucidate the molecular pathways that control β-cell growth we screened ∼2,400 bioactive compounds for rat β-cell replication-modulating activity. Numerous hit compounds impaired or promoted rat β-cell replication, including CC-401, an advanced clinical candidate previously characterized as a c-Jun N-terminal kinase (JNK) inhibitor. Surprisingly, CC-401 induced rodent (in vitro and in vivo) and human (in vitro) β-cell replication via dual specificity tyrosine-phosphorylation-regulated kinases (DYRK1A/B) inhibition. In contrast to rat β-cells, which were broadly growth responsive to compound treatment, human β-cell replication was only consistently induced by DYRK1A/B inhibitors. This effect was enhanced by simultaneous glycogen synthase kinase-3β (GSK-3β) or transforming growth factor-β (ALK5/TGF-β) inhibition. Prior work emphasized DYRK1A/B inhibition-dependent activation of nuclear factor of activated T-cells (NFAT) as the primary mechanism of human β-cell replication induction. However, inhibition of NFAT activity had limited impact on CC-401-induced β-cell replication. Consequently, we investigated additional effects of CC-401-dependent DYRK1A/B inhibition. Indeed, CC-401 inhibited DYRK1A-dependent phosphorylation/stabilization of the β-cell replication-inhibitor p27Kip1. Additionally, CC-401 increased expression of numerous replication-promoting genes normally suppressed by the dimerization partner, RB-like, E2F and multi-vulval class B (DREAM) complex, which depends upon DYRK1A/B activity for integrity, including MYBL2 and FOXM1. In summary, we present a compendium of compounds as a valuable resource for manipulating the signaling pathways that control β-cell replication and leverage a novel DYRK1A/B inhibitor (CC-401) to expand our understanding of the molecular pathways that control β-cell growth.

    View details for PubMedID 29514186

  • Zinc-Chelating Small Molecules Preferentially Accumulate and Function within Pancreatic β Cells. Cell chemical biology Horton, T. M., Allegretti, P. A., Lee, S., Moeller, H. P., Smith, M., Annes, J. P. 2018


    Diabetes is a hyperglycemic condition characterized by pancreatic β-cell dysfunction and depletion. Whereas methods for monitoring β-cell function in vivo exist, methods to deliver therapeutics to β cells are lacking. We leveraged the rare ability of β cells to concentrate zinc to preferentially trap zinc-binding molecules within β cells, resulting in β-cell-targeted compound delivery. We determined that zinc-rich β cells and islets preferentially accumulated TSQ (6-methoxy-8-p-toluenesulfonamido-quinoline) in a zinc-dependent manner compared with exocrine pancreas. Next, we asked whether appending a zinc-chelating moiety onto a β-cell replication-inducing compound was sufficient to confer preferential β-cell accumulation and activity. Indeed, the hybrid compound preferentially accumulated within rodent and human islets in a zinc-dependent manner and increased the selectivity of replication-promoting activity toward β cells. These data resolve the fundamental question of whether intracellular accumulation of zinc-chelating compounds is influenced by zinc content. Furthermore, application of this principle yielded a proof-of-concept method for β-cell-targeted drug delivery and bioactivity.

    View details for PubMedID 30527998

  • The IFN-lambda-IFN-lambda R1-IL-10R beta Complex Reveals Structural Features Underlying Type III IFN Functional Plasticity IMMUNITY Mendoza, J. L., Schneider, W. M., Hoffmann, H., Vercauteren, K., Jude, K. M., Xiong, A., Moraga, I., Horton, T. M., Glenn, J. S., de Jong, Y. P., Rice, C. M., Garcia, K. C. 2017; 46 (3): 379-392


    Type III interferons (IFN-λs) signal through a heterodimeric receptor complex composed of the IFN-λR1 subunit, specific for IFN-λs, and interleukin-10Rβ (IL-10Rβ), which is shared by multiple cytokines in the IL-10 superfamily. Low affinity of IL-10Rβ for cytokines has impeded efforts aimed at crystallizing cytokine-receptor complexes. We used yeast surface display to engineer a higher-affinity IFN-λ variant, H11, which enabled crystallization of the ternary complex. The structure revealed that IL-10Rβ uses a network of tyrosine residues as hydrophobic anchor points to engage IL-10 family cytokines that present complementary hydrophobic binding patches, explaining its role as both a cross-reactive but cytokine-specific receptor. H11 elicited increased anti-proliferative and antiviral activities in vitro and in vivo. In contrast, engineered higher-affinity type I IFNs did not increase antiviral potency over wild-type type I IFNs. Our findings provide insight into cytokine recognition by the IL-10R family and highlight the plasticity of type III interferon signaling and its therapeutic potential.

    View details for DOI 10.1016/j.immuni.2017.02.017

    View details for Web of Science ID 000396818100011

  • Modification by covalent reaction or oxidation of cysteine residues in the tandem-SH2 domains of ZAP-70 and Syk can block phosphopeptide binding BIOCHEMICAL JOURNAL Visperas, P. R., Winger, J. A., Horton, T. M., Shah, N. H., Aum, D. J., Tao, A., Barros, T., Yan, Q., Wilson, C. G., Arkin, M. R., Weiss, A., Kuriyan, J. 2015; 465: 149-161


    Zeta-chain associated protein of 70 kDa (ZAP-70) and spleen tyrosine kinase (Syk) are non-receptor tyrosine kinases that are essential for T-cell and B-cell antigen receptor signalling respectively. They are recruited, via their tandem-SH2 (Src-homology domain 2) domains, to doubly phosphorylated immunoreceptor tyrosine-based activation motifs (ITAMs) on invariant chains of immune antigen receptors. Because of their critical roles in immune signalling, ZAP-70 and Syk are targets for the development of drugs for autoimmune diseases. We show that three thiol-reactive small molecules can prevent the tandem-SH2 domains of ZAP-70 and Syk from binding to phosphorylated ITAMs. We identify a specific cysteine residue in the phosphotyrosine-binding pocket of each protein (Cys39 in ZAP-70, Cys206 in Syk) that is necessary for inhibition by two of these compounds. We also find that ITAM binding to ZAP-70 and Syk is sensitive to the presence of H2O2 and these two cysteine residues are also necessary for inhibition by H2O2. Our findings suggest a mechanism by which the reactive oxygen species generated during responses to antigen could attenuate signalling through these kinases and may also inform the development of ZAP-70 and Syk inhibitors that bind covalently to their SH2 domains.

    View details for DOI 10.1042/BJ20140793

    View details for Web of Science ID 000351685300012

    View details for PubMedID 25287889