Janne Johansson Group
Protein aggregation from a biomedical perspective
Our research group works on mechanisms of protein aggregation in disease, development of protein drugs, and protein assembly in spider silk formation. This broad approach has so far generated synthetic proteins for treatment of lung disease, identification of a chaperone domain that prevents amyloid fibril formation of proteins related to Alzheimers disease and lung fibrosis, a detailed understanding of protein aggregation in spider silk formation, and discovery of a novel way to make artificial spider silk for biomedical applications.
Early work revealed that surfactant protein C (SP-C) - the most hydrophobic polypeptide identified in mammalians - can convert from its native transmembrane alpha-helix into amyloid-like beta-sheet polymers. Surprisingly, the SP-C helix is built from residues that have very high intrinsic tendency to form a beta-strand, and the same phenomenon was found in the amyloid beta-peptide (Abeta) associated with Alzheimers disease and the prion protein underlying spongiform encephalopathies.
Based on this observation we hypothesized that stabilization of the helical state is a means to prevent amyloid fibril formation. This is strongly supported by our findings that designed ligands, which stabilize the helical form of Abeta reduce its toxicity to hippocampal slices, and improve life-span and locomotor activity in transgenic flies that over-express Abeta in the CNS. The same type of reasoning has resulted in the design of a thermodynamically stable SP-C analogue, which can be synthesized in large amounts without aggregation and is now in clinical trials for treatment of respiratory disease in premature infants.
The inherent instability of the SP-C alpha-helix raises questions about its secondary structure formation in vivo. We have discovered that a BRICHOS domain present in the SP-C precursor protein works as an intramolecular chaperone that prevents aggregation during SP-C biosynthesis. Intriguingly, mutations that give rise to lung fibrosis are localized in this chaperone domain. We have recently determined the first crystal structure of a BRICHOS domain and explained how mutations can inactivate the BRICHOS chaperone function. We have also shown that the BRICHOS domain efficiently prevents Abeta fibril formation by keeping it in a soluble, monomeric state. These data suggest that formation of amyloid due to chaperone malfunction is involved in human diseases, and that the BRICHOS domain may be harnessed for anti-amyloid therapy.
Spider silk is formed from proteins - spidroins - that undergo a conversion from soluble conformations to insoluble beta-sheet polymers, thus resembling the mechanisms that underlie amyloid disease. Our group has identified recombinant miniature spidroins that spontaneously form macroscopic silk-like fibers, and suggested a molecular explanation as to how the spidroin N-terminal domain confers solubility and controls assembly by acting as a pH dependent relay. These insights may enable design of customized biomaterials and novel ways to control protein aggregation.
Our current work is focused on studying the anti-amyloid properties of BRICHOS in animal (eg Drosophila) and cell models of amyloid disease, detailed studies of structure and function of recombinant BRICHOS domains, mechanisms involved in physiological regulation of spiders silk formation, and evaluation of artificial spider silk for cell culture and tissue engineering.
|Jenny Presto||PhD, Assistant Professor|
|Anna Rising||PhD, Assistant Professor, Lecturer|
|Nina Kronqvist||PhD, Postdoc|
|Henrik Biverstål||PhD, Postdoc|
|Lisa Dolfe||PhD student|
|Erik Hermansson||PhD student|
Magnus Gustafsson, 2000: Palmitoylation and amyloid fibril formation of lung surfactant protein C.
Shahparak Zaltash, 2000: Pulmonary surfactant proteins B and C. Molecular organisation and involvement in respiratory disease.
Yuqin Wang, 2001: Protein and lipid interactions of mammalian antibacterial polypeptides.
Waltteri Hosia, 2004: Molecular mechanisms in amyloid fibril formation.
Prediction of amyloid fibril-forming proteins.
J. Biol. Chem. 2001 Apr;276(16):12945-50
Molecular basis for amyloid fibril formation and stability.
Proc. Natl. Acad. Sci. U.S.A. 2005 Jan;102(2):315-20
Macroscopic fibers self-assembled from recombinant miniature spider silk proteins.
Biomacromolecules 2007 May;8(5):1695-701
Alpha-helix targeting reduces amyloid-beta peptide toxicity.
Proc. Natl. Acad. Sci. U.S.A. 2009 Jun;106(23):9191-6
Self-assembly of spider silk proteins is controlled by a pH-sensitive relay.
Nature 2010 May;465(7295):236-8
BRICHOS domain associated with lung fibrosis, dementia and cancer--a chaperone that prevents amyloid fibril formation?
FEBS J. 2011 Oct;278(20):3893-904
High-resolution structure of a BRICHOS domain and its implications for anti-amyloid chaperone activity on lung surfactant protein C.
Proc. Natl. Acad. Sci. U.S.A. 2012 Feb;109(7):2325-9
Recombinant spider silk matrices for neural stem cell cultures.
Biomaterials 2012 Nov;33(31):7712-7
pH-dependent dimerization of spider silk N-terminal domain requires relocation of a wedged tryptophan side chain.
J. Mol. Biol. 2012 Sep;422(4):477-87
BRICHOS domains efficiently delay fibrillation of amyloid β-peptide.
J. Biol. Chem. 2012 Sep;287(37):31608-17