Human serum albumin fusion protein as therapeutics for targeting amyloid beta in Alzheimer's diseases

Hyperphosphorylated tau targeting human serum albumin Fusion protein as therapeutics for Alzheimer's diseases

Introduction

Neurofibrillary tangles (NFTs) are composed of hyperphosphorylated forms of microtubule-associated protein tau (Tau), which is responsible for neurodegeneration in Alzheimer's disease (AD). The hippocampal region has been a major focus of AD research because the deposits of phosphorylated tau protein in these regions are correlated with early memory deficits. Despite extensive studies, therapeutic strategies to reduce tau hyperphosphorylation and NFTs deposition remain unclear. AL04, a recently developed recombinant fusion protein comprising Cystatin C, human serum albumin, and a novel blood brain barrier (BBB) penetrating peptide, is currently under investigation. Previous studies have demonstrated its effectiveness in reducing amyloid beta plaques in AD mouse model.

Methods

In this study, we investigated the effects of AL04 on lowering hyperphosphorylated tau and NFTs in JNPL3 mouse model harboring human tau-P301L mutation. 3-month-old female mice intraperitoneally received AL04 (5 mg/kg) or PBS treatment every other week for 24 weeks. We used confocal microscopy and western blot to visualize and analyze changes in hyperphosphorylated tau Ser202/Thr205 labeled with AT8 antibody in the brain.

Results

We found that the AL04 treatment decreases hyperphosphorylated tau at PP2A-sensitive epitope Ser202/Thr205 in the hippocampus of the brain. In the brain lysates of AL04 treated mice, we observed the reduction of I2PP2A, inhibitor of PP2A, and the induction of autophagy receptor proteins such as SQSTM-1/p62 and OPTN.

Conclusion

Our data suggests that AL04 can be used as an AD prophylactic/therapeutic agent as it lowers the hyperphosphorylated tau by downregulating I2PP2A. We also propose that AL04 can induce the degradation of hyperphosphorylated tau aggregates through the upregulation of the autophagy pathway.

Optimization of Protein Folding for Improved Secretion of Human Serum Albumin Fusion Proteins in Saccharomyces cerevisiae

The successful expression and secretion of recombinant proteins in cell factories significantly depend on the correct folding of nascent peptides, primarily achieved through disulfide bond formation. Thus, optimizing cellular protein folding is crucial, especially for proteins with complex spatial structures. In this study, protein disulfide isomerases (PDIs) from various species were introduced into Saccharomyces cerevisiae to facilitate proper disulfide bond formation and enhance recombinant protein secretion. The impacts of these PDIs on recombinant protein production and yeast growth metabolism were evaluated by substituting the endogenous PDI1. Heterologous PDIs cannot fully compensate the endogenous PDI. Furthermore, protein folding mediators, PDI and ER oxidoreductase 1 (Ero1), from different species were used to increase the production of complex human serum albumin (HSA) fusion proteins. The validated folding mediators were then introduced into unfolded protein response (UPR)-optimized strains, resulting in a 7.8-fold increase in amylase-HSA and an 18.2-fold increase in albiglutide compared with the control strain. These findings provide valuable insights for optimizing protein folding and expressing HSA-based drugs.

Characterization of Cysteine Cathepsin Expression in the Central Nervous System of Aged Wild-Type and Cathepsin-Deficient Mice

The association of cathepsin proteases in neurobiology is increasingly recognized. Our previous studies indicated that cathepsin-K-deficient (Ctsk−/−) mice have learning and memory impairments. Alterations in cathepsin expression are known to result in compensatory changes in levels of related cathepsins. To gain insight into the therapeutic usefulness of cathepsin inhibitors in aging individuals with osteoporosis or neurodegenerative diseases, we studied for variations in cathepsin expression and activity in aged (18–20 months) versus young (5–7 months) wild-type (WT) and cathepsin-deficient mice brains. There were age-dependent increases in cathepsin B, D, and L and cystatin C protein levels in various brain regions, mainly of WT and Ctsk−/− mice. This corresponded with changes in activity levels of cathepsins B and L, but not cathepsin D. In contrast, very little age-dependent variation was observed in cathepsin-B- and cathepsin-L-deficient mouse brain, especially at the protein level. The observed alterations in cathepsin protein amounts and activity are likely contributing to changes in important aging-related processes such as autophagy. In addition, the results provide insight into the potential impact of cathepsin inhibitor therapy in aged individuals, as well as in long-term use of cathepsin inhibitor therapy.