The effects of α-RAGE, Streptolysin and Perforin on neuronal Amyloid-β internalization associated with Alzheimer's disease

Abstract

Since the disease was first discovered and defined by the German neuropathologist Alois Alzheimer in 1906, Alzheimer's disease (AD) has been referred to as one of the most detrimental neuronal disorders of mankind. Up to date, it is one of the major topics of modern neuroscience with no cure yet discovered. The number of people diagnosed with AD is likely to increase in the future if healthcare do not improve clinical treatments for patients in counteracting the development of the disease. Comprehensive studies regarding the effects of amyloid-β (aβ) on brains of diagnosed AD patients are in progress worldwide. Studies focused on the mechanisms of neuronal aβ internalization are crucial for understanding the fundamental mechanisms of AD development. In this study, the endocytotic mechanisms of human SH-SY5Y neuroblastoma cells and human primary cortical neurons were altered in order to analyze the internalization of two different aβ variants; aβ-40 and aβ-42. The use of α-RAGE antibodies and the cytolytic proteins streptolysin and perforin resulted in distinct experimental outcomes depending on the type of aβ peptide used. Significant differences between aβ-40 and aβ-42 regarding colocalization of peptides with mitochondria, endoplasmic reticulum (ER) and lysosomes were observed. Further more, results showed that α-RAGE had a prominent effect on the endocytosis of aβ-42 in human SH-SY5Y neuroblastoma cells. α-RAGE did not have the biological property to act as a complete blocking antibody but mediated significantly decreased rates of endocytosis. SLO mainly indicated that passive diffusion of aβ peptides to the intracellular compartment is possible. Effects of perforin resulted in colocalization of aβ-40 and aβ-42 with nuclei of human primary cortical neurons.

Popular Abstract

Alzheimer's Disease - The Brain's Ultimate Horror

Since it was first defined in 1906, Alzheimer's disease has been described as one of the worst brain disorders of mankind with no cure yet discovered. What causes this disease? What damages the brain? And what is the cure? Throughout the decades, science has tried to answer these crucial questions. It is now known that some types of proteins can stick together and damage the nerve cells of the brain. This in turn leads to cell death and loss of brain functions such as loss of memory and less ability of using the muscles of the body. Even though medication for counteracting this disease currently exists, the outcome is a certain death.

One of the main actors in this horror story is the short protein called amyloid-beta (aβ) which causes the disease. There are different types of this protein which exist in nerve cells generally known as neurons, but the complete function of this protein is not yet known. Neurons of the brain produce the protein, release it and can also take it up from the surroundings into the cell body. Inside the neuron, the protein can act as a toxic substance which causes stress for the cell and eventually kills it.

Depending on the number of amino acids, the building blocks of which proteins are made of, different types of aβ proteins have different ability to stick together. Aβ proteins consisting of forty amino acids (aβ-40) and forty-two amino acids (aβ-42) are both known to be involved in Alzheimer's disease. The protein consisting of forty-two amino acids is considered to be the most detrimental type for neurons.

What does actually happen to the toxic protein?
Once aβ is in the surroundings of the neurons, the cells can use different ways of taking up the toxic protein. The ways of uptake can be investigated using certain types of nerve cells. Common types of neurons used are cells from the cancer type called neuroblastoma and neurons from human brains. These types of cells were cultured and treated with aβ-40 and aβ-42 while using different substances which affected the cells in their uptake of these toxic proteins. Treated neurons were stained with different luminous dyes for distinguishing cellular structures by using a laser microscope. The outcome of experiments showed that the cells had indeed been affected in their uptake of aβ-40 and aβ-42. There were even differences in the amount of aβ-40 that cells took up compared to aβ-42, showing that neurons could distinguish between the two different types of aβ. Furthermore, different parts within the neurons were shown to be affected by the uptake of these proteins. These findings can be used in the development of future medication against Alzheimer's disease by the production of drugs which can act against the ability of neurons to take up aβ proteins.

New findings regarding the ways neurons take up toxic proteins such as aβ are crucial in the process of establishing therapies and treatments. These findings will lead us on the path towards finding the cure for Alzheimer's disease. This master's degree project is an important step on the way. I am the story teller and for every discovery made, a page is turned towards the final chapter of this horror story.



Advisor: Homira Behbahani
Master's Degree Project, 45 credits in Neurobiology, 2014
Department of Biology, Lund University

• author: Khanbolouki, Mahbåd
• supervisor: Homira Behbahani
• organization: Degree Projects in Molecular Biology
• course: MOBN29 20141
• year: 2015
• type: H2 - Master's Degree (Two Years)
• subject: Biology and Life Sciences
• keywords: Alzheimer, amyloid-β, streptolysin, perforin, endocytosis, NK cells, RAGE, APP
• language: English
• id: 5313920
• date added to LUP: 2015-04-24 13:56:48
• date last changed: 2015-04-24 13:56:48