Mechanism for the activation of the anaplastic lymphoma kinase receptor.

Anaplastic lymphoma kinase (ALK) is a receptor tyrosine kinase (RTK) that regulates important functions in the central nervous system. The ALK gene is a hotspot for chromosomal translocation events that result in several fusion proteins that cause a variety of human malignancies. Somatic and germline gain-of-function mutations in ALK were identified in paediatric neuroblastoma.

Identification of a biologically active fragment of ALK and LTK-Ligand 2 (augmentor-α).

Elucidating the physiological roles and modes of action of the recently discovered ligands (designated ALKAL1,2 or AUG-α,β) of the receptor tyrosine kinases Anaplastic Lymphoma Kinase (ALK) and Leukocyte Tyrosine Kinase (LTK) has been limited by difficulties in producing sufficient amounts of the two ligands and their poor stability. Here we describe procedures for expression and purification of AUG-α and a deletion mutant lacking the N-terminal variable region. Detailed biochemical characterization of AUG-α by mass spectrometry shows that the four conserved cysteines located in the augmentor domain (AD) form two intramolecular disulfide bridges while a fifth, primate-specific cysteine located in the N-terminal variable region mediates dimerization through formation of a disulfide bridge between two AUG-α molecules.

Alk and Ltk ligands are essential for iridophore development in zebrafish mediated by the receptor tyrosine kinase Ltk.

Anaplastic lymphoma kinase (Alk) and leucocyte tyrosine kinase (Ltk) were identified as "orphan" receptor tyrosine kinases (RTKs) with oncogenic potential. Recently ALKAL1 and ALKAL2 (also named "augmentor-β" and "augmentor-α" or "FAM150A" and "FAM150B," respectively) were discovered as physiological ligands of Alk and Ltk. Here, we employ zebrafish as a model system to explore the physiological function and to characterize in vivo links between Alk and Ltk with their ligands.

Distinct cellular properties of oncogenic KIT receptor tyrosine kinase mutants enable alternative courses of cancer cell inhibition.

Large genomic sequencing analysis as part of precision medicine efforts revealed numerous activating mutations in receptor tyrosine kinases, including KIT. Unfortunately, a single approach is not effective for inhibiting cancer cells or treating cancers driven by all known oncogenic KIT mutants. Here, we show that each of the six major KIT oncogenic mutants exhibits different enzymatic, cellular, and dynamic properties and responds distinctly to different KIT inhibitors.

Augmentor α and β (FAM150) are ligands of the receptor tyrosine kinases ALK and LTK: Hierarchy and specificity of ligand-receptor interactions.

Receptor tyrosine kinases (RTKs) are a class of cell surface receptors that, upon ligand binding, stimulate a variety of critical cellular functions. The orphan receptor anaplastic lymphoma kinase (ALK) is one of very few RTKs that remain without a firmly established protein ligand. Here we present a novel cytokine, FAM150B, which we propose naming augmentor-α (AUG-α), as a ligand for ALK.

The strength and cooperativity of KIT ectodomain contacts determine normal ligand-dependent stimulation or oncogenic activation in cancer.

The receptor tyrosine kinase KIT plays an important role in development of germ cells, hematopoietic cells, and interstitial pacemaker cells. Oncogenic KIT mutations play an important "driver" role in gastrointestinal stromal tumors, acute myeloid leukemias, and melanoma, among other cancers. Here we describe the crystal structure of a recurring somatic oncogenic mutation located in the C-terminal Ig-like domain (D5) of the ectodomain, rendering KIT tyrosine kinase activity constitutively activated.

Structural basis for KIT receptor tyrosine kinase inhibition by antibodies targeting the D4 membrane-proximal region.

Somatic oncogenic mutations in the receptor tyrosine kinase KIT function as major drivers of gastrointestinal stromal tumors and a subset of acute myeloid leukemia, melanoma, and other cancers. Although treatment of these cancers with tyrosine kinase inhibitors shows dramatic responses and durable disease control, drug resistance followed by clinical progression of disease eventually occurs in virtually all patients. In this report, we describe inhibitory KIT antibodies that bind to the membrane-proximal Ig-like D4 of KIT with significant overlap with an epitope in D4 that mediates homotypic interactions essential for KIT activation.

Routes to covalent catalysis by reactive selection for nascent protein nucleophiles.

Reactivity-based selection strategies have been used to enrich combinatorial libraries for encoded biocatalysts having revised substrate specificity or altered catalytic activity. This approach can also assist in artificial evolution of enzyme catalysis from protein templates without bias for predefined catalytic sites. The prevalence of covalent intermediates in enzymatic mechanisms suggests the universal utility of the covalent complex as the basis for selection.