Abnormal activation of canonical Wnt/β-catenin signaling is implicated in many diseases including cancer. As a result, therapeutic agents that disrupt this signaling pathway have been highly sought after. Triptonide is a key bioactive small molecule identified in a traditional Chinese medicine named Tripterygium wilfordii Hook F., and it has a broad spectrum of biological functions. Here we show that triptonide can effectively inhibit canonical Wnt/β-catenin signaling by targeting the downstream C-terminal transcription domain of β-catenin or a nuclear component associated with β-catenin. In addition, triptonide treatment robustly rescued the zebrafish “eyeless” phenotype induced by GSK-3β antagonist 6-bromoindirubin-30-oxime (BIO) for Wnt signaling activation during embryonic gastrulation. Finally, triptonide effectively induced apoptosis of Wnt-dependent cancer cells, supporting the therapeutic potential of triptonide.

Hematopoietic protein-1 (Hem-1) is a hematopoietic cell–specific actin-regulatory protein. Loss-of-function (LOF) variants in the NCKAP1L gene encoding Hem-1 have recently been found to result in primary immunodeficiency disease (PID) in humans, characterized by recurring respiratory infections, asthma, and high mortality. However, the mechanisms of how Hem-1 variants result in PID are not known. In this study, we generated constitutive and myeloid cell–specific Nckap1l-KO mice to dissect the importance of Hem-1 in lung immunity. We found that Hem-1–deficient mice accumulated excessive surfactant and cell debris in airways (pulmonary alveolar proteinosis) due to impaired development of alveolar macrophages (AMs) and reduced expression of the AM differentiation factor Pparg. Residual Hem-1–deficient AMs shifted to a proinflammatory phenotype, and Hem-1–deficient neutrophils and monocytes failed to migrate normally. Myeloid cell–specific Hem-1–deficient mice exhibited increased morbidity following influenza A virus or Streptococcus pneumoniae challenge. These results provide potential mechanisms for how LOF variants in Hem-1 result in recurring respiratory diseases.

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Canonical Wnt/β-catenin signaling plays important roles during vertebrate heart development and inhibition of this pathway has been shown to improve injured heart repair by promoting cardiac progenitor cells’ differentiation. Despite extensive research, to date, no approved Wnt inhibitors are available in clinic. Triptonide is a key bioactive small molecule identified in a traditional Chinese medicine named Tripterygium wilfordii Hook F., and its cellular target has not been identified. Here we showed that triptonide effectively inhibited canonical Wnt/β-catenin signaling by targeting a very downstream nuclear component associated with c-termini-transaction domain of β-catenin. Tripterygium wilfordii Hook F., which contains triptonide, has been traditionally used in clinic in China, suggesting that triptonide may have ideal drug properties. Our discovery of triptonide as an effective Wnt inhibitor may represent an important step in identification of bioactive small molecule drugs to stimulate endogenous cardiac progenitor cells for cardiac repair.

Hematopoietic protein-1 is a hematopoietic cell specific member of the actin-regulatory WAVE complex 2, which acts downstream of multiple immune receptors to stimulate F-actin nucleation. Loss-of-function mutations in the gene encoding Hem-1 (NCKAP1L) have recently been found to result in Primary Immunodeficiency Disease (PID) in humans, characterized by recurrent bacterial and viral respiratory infections, asthma, skin infections, otitis media, and bacteremia. However, the cellular and molecular mechanisms of how loss of Hem-1 results in PID are not known. In this study, we generated constitutive and B cell specific Nckap1l knockout mice using the Cre-LoxP system to dissect the importance of Hem-1 in B cell development and functions. Mice with constitutive deletions of the NCKAP1L gene are severely immunodeficient, characterized by reduced total B and T cells, dysregulated cytokine production and impaired neutrophil migration. To determine why B cells are reduced in the mouse, we bred Nckap1lfloxed mice to Mb1Cre which expresses Cre throughout B cell development. Utilizing flow cytometry, we found that B cell specific deletion of Hem-1 in Nckap1lfl/fl Mb1Cre mice resulted in a reduction in mature B cells in the bone marrow, reduced follicular and marginal zone B cells in the spleen, and reduced innate-like B1a cells. Peripheral B cells from Hem1fl/fl Mb1Cre mice had decreased abilities to migrate to lymphoid tissues in vivo, and altered antibody production following immunization with T-dependent and T-independent immunogens. These results suggest that Hem-1 is essential for normal B cell development and Ab production, and provide novel information regarding why mutations in NCKAP1L result in severe immunodeficiency in humans.