There is an urgent need for novel
therapeutic approaches to treat
Alzheimer’s disease (AD) with the ability to both alleviate
the clinical symptoms and halt the progression of the disease. AD
is characterized by the accumulation of amyloid-β (Aβ)
peptides which are generated through the sequential proteolytic cleavage
of the amyloid precursor protein (APP). Previous studies reported
that Mint2, a neuronal adaptor protein binding both APP and the γ-secretase
complex, affects APP processing and formation of pathogenic Aβ.
However, there have been contradicting results concerning whether
Mint2 has a facilitative or suppressive effect on Aβ generation.
Herein, we deciphered the APP-Mint2 protein–protein interaction
(PPI) via extensive probing of both backbone H-bond and side-chain
interactions. We also developed a proteolytically stable, high-affinity
peptide targeting the APP-Mint2 interaction. We found that both an
APP binding-deficient Mint2 variant and a cell-permeable PPI inhibitor
significantly reduced Aβ42 levels in a neuronal in vitro model of
AD. Together, these findings demonstrate a facilitative role of Mint2
in Aβ formation, and the combination of genetic and pharmacological
approaches suggests that targeting Mint2 is a promising therapeutic
strategy to reduce pathogenic Aβ levels.
Despite the recent advances in cancer therapeutics, highly aggressive cancer forms, such as glioblastoma (GBM), have still very low survival rates. The intracellular scaffold protein syntenin, comprising two PDZ domains, has emerged as a novel therapeutic target in highly malignant phenotypes including GBM. Here, we report the development of a novel, highly potent and metabolically stable peptide inhibitor of syntenin, KSL-128114, which binds the PDZ1 domain of syntenin with nanomolar affinity. KSL-128114 is resistant towards degradation in human plasma and mouse hepatic microsomes, and displays a global PDZ domain selectivity for syntenin. An X-ray crystal structure reveals that KSL-128114 interacts with syntenin PDZ1 in an extended noncanonical binding mode. Treatment with KSL-128114 showed an inhibitory effect on primary GBM cell viability and significantly extends survival time in a patient-derived xenograft mouse model. Thus, KSL-128114 is a novel promising candidate with therapeutic potential for highly aggressive tumors, such as GBM.
All proteins contain characteristic backbones formed of consecutive amide bonds, which can engage in hydrogen bonds. However, the importance of these is not easily addressed by conventional technologies that only allow for side-chain substitutions. By contrast, technologies such as nonsense suppression mutagenesis and protein ligation allow for manipulation of the protein backbone. In particular, replacing the backbone amide groups with ester groups, that is, amide-to-ester mutations, is a powerful tool to examine backbone-mediated hydrogen bonds. In this minireview, we showcase examples of how amide-to-ester mutations can be used to uncover pivotal roles of backbone-mediated hydrogen bonds in protein recognition, folding, function, and structure.
Targeting
multiprotein receptor complexes, rather than receptors
directly, is a promising concept in drug discovery. This is particularly
relevant to the GABAB receptor complex, which plays a prominent
role in many brain functions and diseases. Here, we provide the first
studies targeting a key protein–protein interaction of the
GABAB receptor complexthe interaction with KCTD
proteins. By employing the μSPOT technology, we first defined
the GABAB receptor-binding epitope mediating the KCTD interaction.
Subsequently, we developed a highly potent peptide-based inhibitor
that interferes with the KCTD/GABAB receptor complex and
efficiently isolates endogenous KCTD proteins from mouse brain lysates.
X-ray crystallography and SEC-MALS revealed inhibitor induced oligomerization
of KCTD16 into a distinct hexameric structure. Thus, we provide a
template for modulating the GABAB receptor complex, revealing
a fundamentally novel approach for targeting GABAB receptor-associated
neuropsychiatric disorders.
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