The role of autophagy in Aβ metabolism and neurodegeneration in Alzheimer’s disease – Per Nilsson group

Research focus

Alzheimer’s disease (AD) is characterized by changes in protein homeostasis which leads to accumulation and aggregation of proteins that are toxic to cells in the brain. In AD, these include amyloid beta peptide (Aβ) and tau protein. Autophagy is a master regulator of proteostasis which maintain and adjust the proteome depending on the environment of the cell. This ensures that misfolded and potentially toxic proteins are degraded and at the same time refill the pool of amino acids that will serve as source for the for synthesis of novel proteins. Autophagy is malfunctioning in the Alzheimer’s disease brain and may therefore contribute to the disease progression.

We are analyzing the mechanism of autophagy in the metabolism of Aβ using state of the art AD mouse models. Using genetic tools, we inhibit autophagy in different neuronal cells. Intriguingly, we have found that when autophagy is deleted in the nerve cells, the extracellular Aβ plaques decrease and Aβ instead accumulates intracellularly. This activates neurodegenerative processes which could be linked to the neurodegeneration taking place in the AD brain. This neurodegeneration is currently being investigated by different genetic and omics approaches.

Aβ levels are increased in both familiar and sporadic AD. In familiar AD, genetic mutations cause the increase in Aβ while in sporadic AD a decreased degradation of Aβ may explain the augmented levels. Neprilysin is the major Aβ-degrading enzyme which is controlled by somatostatin receptor (SSTR) signaling. Our aim is to identify blood-brain-barrier-permeable SSTR agonists that activates neprilysin in high through put screens to lower Ab levels.

Publications

Selected publications

Staff and contact

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Simone Tambaro research

Team members

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Jack Lloyd Badman

Postdoctoral studies

Wenjun Li

Postdoctoral studies

I am currently a Senior Research Specialist / Docent (Associate Professor) at the Karolinska Institutet, where I lead an independent research line focused on elucidating the molecular and cellular mechanisms underlying Alzheimer's disease (AD). My research is primarily centered on identifying and characterizing novel target proteins implicated in the onset and progression crucial of this neurodegenerative condition, with the ultimate goal of developing more effective therapeutic strategies. 

My academic training began in Italy, where I obtained a bachelor's degree in 2001 followed by a PhD in Neuroscience from University of Cagliari (2007-2010). Subsequently, I pursued a postdoctoral research at the University of Southern California (USC), USA (2010-2012). After, I was awarded a Marie Curie Postdoctoral Research Fellowship for the PET-BRAIN project (2012-2014), conducted in collaboration with Pharmaness-Neuroscienze (Italy) and the University of Aberdeen (UK).

My current work involves investigating the role of the intramembrane signal peptide peptidase-like proteins (SPPLs) in particular SPPL2b and SPPL2a in AD pathology. Utilizing advanced animal models of AD, particularly the APP-knock-in mouse model AppNL-G-F, my research aims to assess the therapeutic potential of targeting SPPL2b. Their investigations extend to examining the role of key pathological hallmarks of AD, such as the accumulation of amyloid-beta (Aβ) plaques and the presence of neuroinflammation within the brain . By focusing on these fundamental aspects of the disease, our work aims to contribute to the development of more effective strategies for diagnosis and treatment. 

 

The Role of SPPL2b in Alzheimer's Disease

SPPL2b has emerged as a promising therapeutic target for AD. SPPL2b is brain-specific and predominantly expressed in the hippocampus and cortex. 

Simone1

SPPL2b structure and substrate proteolysis.

SPPL2b belongs to the same protein family as Presenilin 1, the catalytic site of gamma secretase complex, and regulates the cleavage of proteins associated with 1) amyloid formation (BRI2, CD74), 2) inflammation (TNFα, Clec7a, and Lox-1), and 3) synaptic function (Neuregulin-1, VAMP2) (13-16) (Figure 1). In particular, the SPPL2b substrate BRI2 has been proposed as an anti-Alzheimer's protein (17). BRI2 is a transmembrane protein, highly expressed in neurons and glia just as SPPL2b. Under physiological conditions, BRI2 interacts with APP, forming a BRI2-APP complex that negatively regulates Aβ production by inhibiting APP processing (18). 

Simone2

SPPL2b brain substrates and expected beneficial effects of SPPL2b inhibition/modulation in AD pathology.

In our lab, we demonstrated that the inhibitory action of BRI2 on APP processing and Aβ generation is more pronounced when SPPL2b-mediated cleavage of BRI2 in the transmembrane region is silenced (Maccioni et al., 2024). This anti-Aβ production role of BRI2 is further supported by a previous study, where BRI2 overexpression led to a reduced secretion of Aβ peptides and Aβ plaque deposition in an AD mouse model. On the other hand, the cleavage of TNFα by SPPL2b is associated with the release of an intracellular fragment, TNFα ICD into the cytosol. TNFα ICD induces the expression of the cytokine interleukin-12 (IL-12) which activates a proinflammatory pathway, inhibition of which has been linked to a reduction in AD pathology and cognitive decline. As mentioned earlier, SPPL2b regulates the synaptic protein VAMP2, and lower levels of VAMP2 in the hippocampus and entorhinal cortex have been associated with cognitive decline and AD. Furthermore, VAMP2 has emerged as a potential marker of synapse degeneration, correlating with CSF AD markers, axonal degeneration markers, and cognitive performance. 

Recent advances from our team have highlighted SPPL2b's critical role in AD, particularly in Aβ pathology and neuroinflammation. Our findings show that SPPL2b inhibition reduces Aβ42, Aβ40, and sAPPβ levels, suggesting its involvement in the early stages of AD. Most importantly, SPPL2b deletion in the AppNL-G-FAD mouse model, led to decreased Aβ42 levels, Aβ plaque deposition, and significant reductions in astrocytosis and microgliosis, indicating less neuroinflammation. Additionally, we performed an in silico screening which has identified 100 potential SPPL2b inhibitors, which will be evaluated in vitro and in vivo, paving the way for a novel pharmacological approach to AD therapy. 

 

The Endocannabinoid System (ECS) and Neurological Disorders

Furthermore, my research explores the involvement of the endocannabinoid system (ECS) in neurological disorders, including Alzheimer's disease and anxiety. We are particularly focused on the immunomodulatory functions of CB2 receptors and the therapeutic potential of cannabinoids in modulating neuroinflammatory processes.

Simone2

Schematic representation of the biphasic effects of THC.

Expertise

As a team, we bring together a diverse and complementary set of skills essential for advancing neuroscience and pharmacological research. We possess extensive expertise in both in vitro and in vivo techniques. This includes nearly all in vitro methods used in studies of brain morphology, immunohistochemistry, and protein analyses. Our methodological strengths also extend to proteomic analysis, molecular neuroscience, and a comprehensive understanding of the molecular mechanisms underlying brain function and disease. In vivo, we have deep experience in behavioral neuroscience, particularly in conducting behavioral tests in animal models of learning, memory, and neuropsychiatric disorders.

 

Funding
My research is supported by national and international funding bodies, including the Alzheimer’s Association, Olle Engkvists Stiftelse, Alzheimerfonden, Demensfonden, Åhlén-Stiftelsen, Gun & Bertil Stohnes Stiftelse, Lindhés Advokatbyrå Stiftelse, and Stiftelsen för Gamla Tjänarinnor.

 

Collaborations
I collaborate with:

  • Assoc. Prof. Per Nilsson (Karolinska Institutet), expert in AD mouse models, especially those used in our studies.
  • Dr. Rajnish Kumar (IIT, India & Karolinska Institutet), specializing in computational modeling and medicinal chemistry for drug development; leads compound screening and optimization for SPPL2b inhibitors.
  • Prof. Tiziana Cabras (University of Cagliari, Italy), collaborator on mass spectrometry-based protein profiling.
  • Dr. Ignazio Piras (TGen, Arizona, USA), provides access to large-scale post-mortem gene expression datasets from consortia including Mayo Clinic, ROSMAP, and Mount Sinai.
  • Prof. Bernd Schröder (Technical University of Dresden, Germany), a leading expert in SPPL biology, supporting our studies with custom SPPL antibodies and mechanistic insights.
  • Prof. Sandra Rebelo (University of Aveiro, Portugal), specialist in BRI2 and AD; I also co-supervise her PhD student, Mariana Vassal.

 

Team Members Involved in This Project

  • Jack Badman
  • Eileen Mac Sweeney
  • Bjorn Bakker
  • Wenjun Li

 

If you are interested in collaboration or are a Master's student seeking thesis opportunities in our lab, please feel free to contact me.