Assistant Investigator, TIGEM
Mechanisms of Neurodegeneration in Lysosomal Storage Disorders
Lysosomal storage disorders (LSDs) are inherited diseases characterized by lysosomal storage and dysfunction. Loss of lysosomal function is associated with severe neurodegeneration, which is the prominent pathological hallmark of LSDs.
One of our major goals is to elucidate how lysosomal dysfunction may specifically affect neuronal function and viability, thus allowing us to determine the neuropathological phenotype observed in LSDs.
In neuronal cells post-Golgi membrane trafficking is highly specialized and is pivotal to sustain key neuronal processes such as neurite outgrowth of developing neurons and synaptic transmission. These processes require a group of proteins called SNAREs to engage and cooperate, as they are a major component of cellular fusion machinery.
In our lab we investigate the functionality of post-Golgi membrane trafficking pathways with particular emphasis on synaptic vesicle recycling in neurons of neurodegenerative LSDs. Specifically, we want to determine whether a mechanistic relationship exists among the functionality of these trafficking pathways, the lysosomal dysfunction and LSD neuropathology. In order to realize these studies, we use both in vivo (mouse models of neurodegenerative LSDs) and in vitro (neuronal cell cultures) model systems.
We also believe that these studies will be instrumental in identifying new therapeutic targets for the treatment of brain lesions in LSDs.
CNS therapy in Lysosomal Storage Disorders
Our second research line allows us to design and test minimally invasive therapeutic approaches, which efficiently treat neuropathology in LSDs. Several LSDs are caused by deficiency of soluble proteins, which may be secreted with different efficiency rates. One of the approaches that we have developed in our lab is based on the modification of these proteins. The purpose of this is to enhance protein secretion from liver and allow efficient cross of the blood-brain barrier (BBB) to target the brain after intravascular administration of a viral vector containing the gene encoding the engineered protein. To test the therapeutic feasibility and efficacy of this therapeutic strategy we are using different animal models of mucopolysaccharidoses (MPSs), a group of LSDs mostly caused by deficits of soluble and secreted lysosomal hydrolases. Adeno-associated virus (AAV) vectors with high tropism to the liver are used as vehicles to systemically target the liver and transform it into a factory organ for the modified enzyme. However, for further clinical applications the modified enzymes may also be directly supplied intravenously as recombinant proteins (enzyme replacement therapy).
A subset of LSDs is caused by the deficit of specific lysosomal membrane proteins. The insolubility of these proteins makes treating these disorders challenging or even unfeasible. In our lab we are also developing novel nanoparticle vectors capable of delivering a membrane protein to the lysosomes of a diseased brain.
Lumbar intratechal injection is an alternative, minimally invasive route for delivering therapeutics to the brain. Additionally we are attempting to identify new AAV serotypes that efficiently target the CNS via the intratechal administration route. We are using wild-type pigs as a large animal model to evaluate the potential clinical translation of therapeutic approaches based on the use of lumbar intratechal delivery of AAVs to treat the brain in LSDs.
Alessandro Fraldi, Andrés D. Klein, Diego L. Medina, and Carmine Settembre (2016). Brain Disorders Due to Lysosomal Dysfunction. Annu. Rev. Neurosci. doi: 10.1146/annurev-neuro-070815-014031
Sorrentino NC, Maffia V, Strollo S, Cacace V, Romagnoli N, Manfredi A, Ventrella D, Dondi F, Barone F, Giunti M, Graham AR, Huang Y, Kalled SL, Auricchio A, Bacci ML, Surace EM, Fraldi A (2016). A Comprehensive Map of CNS Transduction by Eight Recombinant Adeno-associated Virus Serotypes Upon Cerebrospinal Fluid Administration in Pigs. Mol Ther. 24(2):276-86.
Sorrentino NC, D’Orsi L, Sambri I, Nusco E, Monaco C, Spampanato C, Polishchuk E, Saccone P, De Leonibus E, Ballabio A and Fraldi A (2013). A highly secreted sulfamidase engineered to cross the blood-brain barrier corrects brain lesions of mice with mucopolysaccharidoses type IIIA. EMBO Mol Med. 5(5): 675–690. doi: 10.1002/emmm.201202083.
Fraldi A, Annunziata F, Lombardi A, Kaiser HJ, Medina DL, Spampanato C, Fedele AO, Polishchuk R, Sorrentino NC, Simons K, Ballabio A (2010). Lysosomal fusion and SNARE function are impaired by cholesterol accumulation in lysosomal storage disorders. EMBO J. 29(21):3607-20. doi: 10.1038/emboj.2010.237.
Fraldi A, Hemsley K, Crawley A, Lombardi A, Lau A, Sutherland L, Auricchio A, Ballabio A, Hopwood J (2007). Functional correction of CNS lesions in an MPS-IIIA mouse model by intracerebral AAV-mediated delivery of sulfamidase and SUMF1 genes. Hum Mol Genet. 16(22):2693-702. doi: 10.1093/hmg/ddm223.