Reply to Comment on "Binding Affinity Determines Substrate Specificity and Enables Discovery of substrates for N-Myristoyltransferases".

In our previously published article, an intriguing enzymology observation with the N-myristoyltransferases (NMT1 and NMT2) led us to conclude that binding affinity is important for determining in vivo substrate specificity and this can explain the vast literature that reports the coimmunoprecipitation of protein-modifying enzymes and their substrates. This understanding also provides a facile method to identify substrate proteins for such enzymes, which we demonstrated by identifying three substrate proteins using existing interactome data for NMT1 and NMT2. Dr.

Binding Affinity Determines Substrate Specificity and Enables Discovery of Substrates for N-Myristoyltransferases.

Kinetic parameters ( and ) derived from the Michaelis-Menten equation are widely used to characterize enzymes. / is considered the catalytic efficiency or substrate specificity of an enzyme toward its substrate. N-Myristoyltransferases (NMTs) catalyze the N-terminal glycine myristoylation of numerous eukaryotic proteins.

A STAT3 palmitoylation cycle promotes T17 differentiation and colitis.

Cysteine palmitoylation (S-palmitoylation) is a reversible post-translational modification that is installed by the DHHC family of palmitoyltransferases and is reversed by several acyl protein thioesterases. Although thousands of human proteins are known to undergo S-palmitoylation, how this modification is regulated to modulate specific biological functions is poorly understood. Here we report that the key T helper 17 (T17) cell differentiation stimulator, STAT3, is subject to reversible S-palmitoylation on cysteine 108.

N-Myristoyltransferase as a Glycine and Lysine Myristoyltransferase in Cancer, Immunity, and Infections.

Protein myristoylation, the addition of a 14-carbon saturated acyl group, is an abundant modification implicated in biological events as diverse as development, immunity, oncogenesis, and infections. N-Myristoyltransferase (NMT) is the enzyme that catalyzes this modification. Many elegant studies have established the rules guiding the catalysis including substrate amino acid sequence requirements with the indispensable N-terminal glycine, and a co-translational mode of action.

NMT1 and NMT2 are lysine myristoyltransferases regulating the ARF6 GTPase cycle.

Lysine fatty acylation in mammalian cells was discovered nearly three decades ago, yet the enzymes catalyzing it remain unknown. Unexpectedly, we find that human N-terminal glycine myristoyltransferases (NMT) 1 and 2 can efficiently myristoylate specific lysine residues. They modify ADP-ribosylation factor 6 (ARF6) on lysine 3 allowing it to remain on membranes during the GTPase cycle.

Novel Lysine-Based Thioureas as Mechanism-Based Inhibitors of Sirtuin 2 (SIRT2) with Anticancer Activity in a Colorectal Cancer Murine Model.

Sirtuin 2 (SIRT2) is a protein lysine deacylase that has been indicated as a therapeutic target for cancer. To further establish the role of SIRT2 in cancers, it is necessary to develop selective and potent inhibitors. Here, we report the facile synthesis of novel lysine-derived thioureas as mechanism-based SIRT2 inhibitors with anticancer activity.

Updates on the epigenetic roles of sirtuins.

Sirtuins are a class of enzyme with NAD-dependent protein lysine deacylase activities. They were initially discovered to regulate transcription and life span via histone deacetylase activities. Later studies expanded their activities to other proteins and acyl lysine modifications.

MENA Confers Resistance to Paclitaxel in Triple-Negative Breast Cancer.

Taxane therapy remains the standard of care for triple-negative breast cancer. However, high frequencies of recurrence and progression in treated patients indicate that metastatic breast cancer cells can acquire resistance to this drug. The actin regulatory protein MENA and particularly its invasive isoform, MENA, are established drivers of metastasis.

MenaINV mediates synergistic cross-talk between signaling pathways driving chemotaxis and haptotaxis.

Directed cell migration, a key process in metastasis, arises from the combined influence of multiple processes, including chemotaxis-the directional movement of cells to soluble cues-and haptotaxis-the migration of cells on gradients of substrate-bound factors. However, it is unclear how chemotactic and haptotactic pathways integrate with each other to drive overall cell behavior. Mena has been implicated in metastasis by driving chemotaxis via dysregulation of phosphatase PTP1B and more recently in haptotaxis via interaction with integrin α5β1.

Parallel In Vivo Assessment of Drug Phenotypes at Various Time Points during Systemic BRAF Inhibition Reveals Tumor Adaptation and Altered Treatment Vulnerabilities.

Purpose: Treatment of BRAF-mutated melanoma tumors with BRAF inhibitor-based therapy produces high response rates, but of limited duration in the vast majority of patients. Published investigations of resistance mechanisms suggest numerous examples of tumor adaptation and signal transduction bypass mechanisms, but without insight into biomarkers that would predict which mechanism will predominate. Monitoring phenotypic response of multiple adaptive mechanisms simultaneously within the same tumor as it adapts during treatment has been elusive.

Tumor Cell-Driven Extracellular Matrix Remodeling Drives Haptotaxis during Metastatic Progression.

Unlabelled: Fibronectin (FN) is a major component of the tumor microenvironment, but its role in promoting metastasis is incompletely understood. Here, we show that FN gradients elicit directional movement of breast cancer cells, in vitro and in vivo Haptotaxis on FN gradients requires direct interaction between α5β1 integrin and MENA, an actin regulator, and involves increases in focal complex signaling and tumor cell-mediated extracellular matrix (ECM) remodeling. Compared with MENA, higher levels of the prometastatic MENA(INV) isoform associate with α5, which enables 3-D haptotaxis of tumor cells toward the high FN concentrations typically present in perivascular space and in the periphery of breast tumor tissue.