TSRI and St. Jude scientists study single 'transformer' proteins with role in cancer

December 21, 2015

LA JOLLA, CA - December 21, 2015 - A new study led by scientists at The Scripps Research Institute (TSRI) and St. Jude Children's Research Hospital shows how a protein involved in cancer twists and morphs into different structures.

"We're studying basic biophysics, but we believe the complexity and rules we uncover for the physics of protein disorder and folding could one day also be used for better designs of therapeutics," said TSRI Associate Professor Ashok Deniz, senior author of the new study along with Richard Kriwacki, faculty member at St. Jude.

The study, published recently in the journal Angewandte Chemie, focuses on a protein called nucleophosmin (NPM1). This protein has many functions and, when mutated, has been shown to interfere with cells' normal tumor suppressing ability. NPM1 has been implicated in cancers such as non-Hodgkin lymphoma and acute myelogenous leukemia.

Previous research led by study collaborators Kriwacki and Diana Mitrea at St. Jude had shown that a section of NPM1, called the N-terminal domain (Npm-N), doesn't have a defined, folded structure. Instead, the protein morphs between two forms: a one-subunit disordered monomer and a five-subunit folded pentamer.

Until now, the mechanism behind this transformation was unknown, but scientists believed this monomer-pentamer equilibrium could be important for the protein's location and functioning in the cell.

To shed light on how this transformation occurred, Deniz and his colleagues used an innovative combination of three techniques--single-molecule biophysics, fluorescence resonance energy transfer (FRET) and circular dichroism--which enabled them to study individual molecules and collections of molecules. Single-molecule methods are especially useful for such studies because they can uncover important information that remains hidden in conventional studies.

Remarkably, the researchers found that the transformation can proceed through more than one pathway. In one pathway, the transformation begins when the cell sends signals to attach phosphoryl groups to NPM1. This modification, called phosphorylation, prompts the ordered pentamer to become disordered and likely causes NPM1 to shuttle outside the cell's nucleus. A meeting with a binding partner can mediate the reverse transformation to a pentamer.

Interestingly, when NPM1 does become a pentamer again under these conditions, which likely causes it to move back to the nucleolus, it takes a different path instead of just retracing its earlier steps.

Priya Banerjee, an American Heart Association-supported postdoctoral research associate at TSRI and the first author of the study, compared these complicated transitions to the morphing of a "Transformers" toy, where a robot can become a car and then a jet. "Phosphorylation and partner-binding are like different cellular switches driving these changes," said Banerjee.

Banerjee said the new study also reveals many intermediate states between monomer and pentamer structures--and that these states can be manipulated or "tuned" by changing conditions such as salt levels, phosphorylation and partner binding, which may explain how cells regulate the protein's multiple functions. The researchers said future studies could shed more light on the biological functions of these different structures and how they might be used in future cancer therapies.

The researchers added that combining the three techniques used in this study, plus a novel protein-labeling technique for single-molecule fluorescence, could be a useful strategy for studying other unstructured, "intrinsically disordered proteins" (IDPs). IDPS are involved in a host of cellular functions, as well as neurodegenerative disease, heart disease, infectious disease, type 2 diabetes and other conditions.
-end-
The study, "Asymmetric Modulation of Protein Order-Disorder Transitions by Phosphorylation and Partner Binding," was supported by the National Institutes of Health (NIH) (grants R01 GM066833, 1R01GM115634, 2R01GM083159 and 2R01CA082491), National Science Foundation (grant MCB1121959), the NIH National Cancer Institute (grant P30CA21765), ALSAC and the American Heart Association. See http://onlinelibrary.wiley.com/doi/10.1002/anie.201507728/full

Scripps Research Institute

Related Protein Articles from Brightsurf:

The protein dress of a neuron
New method marks proteins and reveals the receptors in which neurons are dressed

Memory protein
When UC Santa Barbara materials scientist Omar Saleh and graduate student Ian Morgan sought to understand the mechanical behaviors of disordered proteins in the lab, they expected that after being stretched, one particular model protein would snap back instantaneously, like a rubber band.

Diets high in protein, particularly plant protein, linked to lower risk of death
Diets high in protein, particularly plant protein, are associated with a lower risk of death from any cause, finds an analysis of the latest evidence published by The BMJ today.

A new understanding of protein movement
A team of UD engineers has uncovered the role of surface diffusion in protein transport, which could aid biopharmaceutical processing.

A new biotinylation enzyme for analyzing protein-protein interactions
Proteins play roles by interacting with various other proteins. Therefore, interaction analysis is an indispensable technique for studying the function of proteins.

Substituting the next-best protein
Children born with Duchenne muscular dystrophy have a mutation in the X-chromosome gene that would normally code for dystrophin, a protein that provides structural integrity to skeletal muscles.

A direct protein-to-protein binding couples cell survival to cell proliferation
The regulators of apoptosis watch over cell replication and the decision to enter the cell cycle.

A protein that controls inflammation
A study by the research team of Prof. Geert van Loo (VIB-UGent Center for Inflammation Research) has unraveled a critical molecular mechanism behind autoimmune and inflammatory diseases such as rheumatoid arthritis, Crohn's disease, and psoriasis.

Resurrecting ancient protein partners reveals origin of protein regulation
After reconstructing the ancient forms of two cellular proteins, scientists discovered the earliest known instance of a complex form of protein regulation.

Sensing protein wellbeing
The folding state of the proteins in live cells often reflect the cell's general health.

Read More: Protein News and Protein Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.