Understanding the molecular basis of Usher syndrome type 1J: the role of functional defects in CIB2

Starting date
September 1, 2016
Duration (months)
24
Departments
Neurosciences, Biomedicine and Movement Sciences
Managers or local contacts
Dell'Orco Daniele

Calcium- and integrin- binding protein 2 (CIB2) is a neuronal calcium sensor recently found to be involved in
Usher syndrome J1 (USH1J), a severe disease leading to profound congenital hearing impairment and
adolescent-onset blindness. Protein localization in both mechanosensory stereocilia of the inner ear hair, retinal
photoreceptors inner and outer segments and pigmented epithelium cells suggest as a common feature of
molecular dysfunction an impairment of the calcium homeostasis. However, dedicated mechanistic studies and
even basic biochemical characterization of the identified pathological CIB2 variants are currently missing. The
proposed project aims at setting the basis for understanding the molecular mechanisms underlying the
dysfunctional forms of CIB2. Recombinant CIB2 will be heterologously expressed and purified in its wild type
and mutant variants and characterized in a comparative fashion. Four mutants will be studied, namely p.E64D,
directly related to USH1, as well as p.F91S, p.C99W and p.I123T, which are involved in non-syndromic
deafness DFNB48. We will clarify whether the effect of mutations is mostly to alter the structural/functional
features of CIB2 itself or rather to perturb the binding to αIIβ integrin, or a combination of both. The effects of
mutations on protein structure/function and protein-protein interactions will be thoroughly investigated by
biochemical and biophysical techniques. The capability of CIB2 variants to physiologically bind Ca2+ will be
measured and the propensity to form supramolecular assemblies will be also investigated, especially focussing
on potential changes in both affinity and kinetics of the interaction with a peptide from αIIβ integrin, in order to
uncover potential hallmarks of disease at a molecular level. Molecular dynamics simulations will be carried out
to highlight the determinants of the interactions at atomistic level.

Project participants

Daniele Dell'Orco
Associate Professor

Activities

Research facilities