Molecular and evolutive bases for the cell adhesion properties of some non-catalytic alpha/beta-hydrolases – MOLADCEL

The main steps of this project are:
1- Generate artificial though biologically relevant forms of the known cell adhesion molecules (and the known partner of one of them) to determine their 3D structures and structure-function relationships.
2- Use these artificial adhesion molecules as baits to fish their unknown genuine partners in selected biological preparations,
3- Improve the content and the bioinformatic tools available in the ESTHER database to analyse and classify the enzyme and adhesion functions of alpha/beta hydrolases,
4- Confront the gathered biological, biophysical and bioinformatical pieces of information to predict the function (enzyme or adhesion?) of newly identified alpha/beta hydrolases,
5- Generate artificial/relevant forms of these new proteins and analyse their structures and functions to validate/invalidate our hypotheses.
(Non-contractual order.)

Recombinant forms of 2 of the 3 cell adhesion molecules targeted by this project and of the know partner of one of them have been generated in eucaryotic cells. The kinetic parameters for formation of the “1rst adhesion molecule – know partner” complex have been determined and found to be consistent with a cell adhesion function; theoretical 3D models of these molecules have been generated; experiments aimed at solve the 3D structure of each partners and the complex are underway. The 2nd adhesion molecule is about to be used as a bait to find its unknown partners from selected biological samples. A similar strategy will be used for the 3rd adhesion molecule when suitable expression yields can be obtained. The ESTHER database has been updated (content) and improved (form and new tools); the beta server has been made available progressively since july 2011 and will be launched officially in august 2012. The new tools made available are aimed at identifying new targets for a structural study of families either poorly known or whose members might display new or dual functions (or both). An initial search has pointed to newly entered alpha/beta hydrolases that could be new cell adhesion molecules. Three candidates have been selected and subjected to bacterial expression trials.

The information which we expect to gather will document the molecular mechanisms used by the alpha/beta hydrolase fold, an ancient structural motif associated with a well-defined enzymatic activity, to evolve into recognition of a proteic partner and cell adhesion. This will allow us to understand why and how some alpha/beta hydrolases display two kinds of activities or have lost the enzyme activity while no other activity has been detected. This will also allow us to predict the function (enzyme or adhesion?) of newly identified members in the family.

- Publication in feb 2012 of a special issue of Protein Pept lett, edited and contributed by the partners of this project and gathering 8 chapters on alpha/beta hydriolase fold proteins (http://www.benthamscience.com/contents-JCode-PPL-Vol-00000019-Iss-00000002.htm).
- One talk and one poster presented during an international meeting (http://www.11che.ru/home.html).
- One original article submitted july 2012 for publication in Chem Biol Interact.
- One original article in preparation, to be submitted sept 2012 for publication in Nucleic Acids Res, Database Issue 2013.

A class of neural cell-adhesion proteins known as cholinesterase-like (ChE-like) cell adhesion molecules has been identified whose members share an extracellular functional domain structurally related to the catalytic domain of the ChEs. A long term collaboration between partners 1 and 2 herein involved has led to document in great details the structural bases and determinants for ChE function and dysfunction and, more recently, those for neurexin recognition by the ChE-like adhesion molecule neuroligin. An occasional collaboration between partners 3 and 1 has led to the latest updating of the ESTHER database, dedicated to gathering and annotating all available information on members of the alpha/beta-hydrolase fold family, headed by the ChE enzymes.

We now plan as a new endeavor to study other ChE-like adhesion molecules, alone and in complex with their respective physiological partners. The development of the nervous system is a complex system that requires cell-adhesion interactions involving axon guidance receptors. In addition to structural characterization of these proteins and the only partner available to date, availability of recombinant soluble forms will allow us to track and identify/characterize the still unknown partners through ligand-fishing and proteomics strategies or alternative strategies if required or better. This will led to functional and structural characterisation of several diversified complexes of a ChE-like adhesion molecule with its specific partner. This will also led to new pieces of information which the ESTHER database can exploit for annotating determinants for cell adhesion and predicting new cell-adhesion or dual-function members within the family. The tight network and interplay between the structural neurobiology and bioinformatics approaches will be a insightful advantage for each individual team and for the whole collaborative project.