Moving lipids : ceramides, glycosphingolipids and the glycolipid transfer protein

Lipid movement in cells occurs by a variety of methods. Lipids diffuse freely along the lateral plane of a membrane and can translocate between the lipid leaflets, either spontaneously or with the help of enzymes. Lipid translocation between the different cellular compartments predominantly takes place through vesicular transport. Specialized lipid transport proteins (LTPs) have also emerged as important players in lipid movement, as well as other cellular processes. In this thesis we have studied the glycolipid transport protein (GLTP), a protein that transports glycosphingolipids (GSLs). While the in vitro properties of GLTP have been well characterized, its cell biological role remains elusive. By altering GSL and GLTP levels in cells, we have extracted clues towards the protein's function. Based on the results presented in this thesis and in previous works, we hypothesize that GLTP is involved in the GSL homeostasis in cells. GLTP most likely functions as a transporter or sensor of newly synthesized glucosylceramide (GlcCer), at or near the site of GlcCer synthesis. GLTP also seems to be involved in the synthesis of globotriacylceramide, perhaps in a manner that is similar to that of the fourphosphate adaptor protein 2, another GlcCer-transporting LTP. Additionally, we have developed and studied a novel method of introducing ceramides to cells, using a solvent-free approach. Ceramides are important lipids that are implicated in several cellular functions. Their role as proapoptotic molecules is particularly evident. Ceramides form stable bilayer structures when complexed with cholesterol phosphocholine (CholPC), a large-headgroup sterol. By adding ceramide/CholPC complexes to the growth medium, various chain length ceramides were successfully delivered to cells in culture. The uptake rate was dependent on the chain length of the ceramide, where shorter lipids were internalized more quickly. The rate of uptake also determined how the cells metabolised the ceramides. Faster uptake favored conversion of ceramide to GlcCer, whereas slower delivery resulted mainly in breakdown of the lipid.

Pinning Down Identity in Social Media: Food Cultural Transfer on Pinterest

This research has been conducted within the realm of where today’s digital media society and the timeless concept of cultural identity overlap. The aim of this thesis is to explore the nature of online cultural identity management. By focusing on the social media platform, Pinterest, this study considers the food-pinning behavior of a group of Americans living in Finland and connects their online actions with their cultural identity. Through an examination of Pinterest as a social space, and even a third place, the relative theoretical literature provides and interesting background for a contemporary discussion on the matter. Literature on food as a cultural marker is also brought into consideration. Using the methods of introspection and an adapted version of virtual ethnography, a study was conducted, and ultimately, the analysis of data obtained from the Pinterest boards of ten individuals shows that the vast majority of food-related information in this setting is US-sourced. A questionnaire provides further insight into the individuals’ Pinterest usage. I argue that pinning is an act of online identity management, whether it is a conscious act or a situational effect, and that using Pinterest maintains and even strengthens these individuals’ cultural identity as Americans. This study adds to current discussions pertaining to transnationalism, globalization, and online cultural identity, as well as opens channels for further research on this dynamic topic, which is needed to understand ourselves as cultural beings in the digital age.

Pinning Down Identity in Social Media: Food Cultural Transfer on Pinterest

This research has been conducted within the realm of where today’s digital media society and the timeless concept of cultural identity overlap. The aim of this thesis is to explore the nature of online cultural identity management. By focusing on the social media platform, Pinterest, this study considers the food-pinning behavior of a group of Americans living in Finland and connects their online actions with their cultural identity. Through an examination of Pinterest as a social space, and even a third place, the relative theoretical literature provides and interesting background for a contemporary discussion on the matter. Literature on food as a cultural marker is also brought into consideration. Using the methods of introspection and an adapted version of virtual ethnography, a study was conducted, and ultimately, the analysis of data obtained from the Pinterest boards of ten individuals shows that the vast majority of food-related information in this setting is US-sourced. A questionnaire provides further insight into the individuals’ Pinterest usage. I argue that pinning is an act of online identity management, whether it is a conscious act or a situational effect, and that using Pinterest maintains and even strengthens these individuals’ cultural identity as Americans. This study adds to current discussions pertaining to transnationalism, globalization, and online cultural identity, as well as opens channels for further research on this dynamic topic, which is needed to understand ourselves as cultural beings in the digital age.