THE IDENTIFICATION AND CHARACTERIZATION OF A GROUP OF ER TPR-CONTAINING ADAPTER PROTEINS

The endoplasmic reticulum (ER) is an organelle responsible for a variety of functions in all eukaryotic cells. Some of these functions are localized to specific regions in the ER, such as the ribosome-studded rough ER sheets or the ribosome-free smooth ER sheets. The smooth ER sheets have the ability to form ER tubules, which extend throughout the cell and make contact with other organelles. In order to accommodate these localized functional regions, a certain degree of heterogeneity and compartmentalization into sub-domains exists within the ER. Since the ER membrane and lumen are contiguous, the compartmentalization of the ER into sub-domain cannot exclusively be created by membrane barriers. Adapter proteins nucleate the formation of protein complexes to create sub-domains in the ER. Tetratricopeptide repeats (TPR) containing proteins are known to organize protein complexes involved in a wide range of cellular processes. While the human genome is predicted to encode ~ 180 TPR proteins, only two have previously been shown to localize to the ER. We hypothesized that there are additional TPR-containing adapter proteins that contribute to the organization or compartmentalization of ER processes. To this end, we screened an in silico library of putative TPR containing proteins from the Regan laboratory (Yale University) to identify proteins that potentially possess an N-terminal ER targeting signal sequence. This screen, combined with additional in silico approaches, identified nine putative ER proteins that contained between three to ten TPR motifs. While some of the identified proteins are soluble ER proteins (i.e. TTC13 and TTC17), others were found to reside in the ER membrane with their TPR domains facing the ER lumen (TMTC1-4). TMTC1 and TMTC2 were found to interact with the ER calcium pump SERCA2B, and TMTC2 with calnexin. Additionally, live cell calcium measurements showed a role for TMTC1 and TMTC2 in calcium homeostasis. Overall, this strategy was successful in identifying novel ER proteins with TPR motifs, and this approach can be applied to identify proteins with specific motifs in the ER or other organelles

The role of UDP-Glc:glycoprotein glucosyltransferase 1 in the maturation of an obligate substrate prosaposin

A natural substrate for UGT1 is confirmed, revealing how the enzyme functions in the calnexin chaperone system as a quality control step in protein folding

THE IDENTIFICATION AND CHARACTERIZATION OF A GROUP OF ER TPR-CONTAINING ADAPTER PROTEINS

The endoplasmic reticulum (ER) is an organelle responsible for a variety of functions in all eukaryotic cells. Some of these functions are localized to specific regions in the ER, such as the ribosome-studded rough ER sheets or the ribosome-free smooth ER sheets. The smooth ER sheets have the ability to form ER tubules, which extend throughout the cell and make contact with other organelles. In order to accommodate these localized functional regions, a certain degree of heterogeneity and compartmentalization into sub-domains exists within the ER. Since the ER membrane and lumen are contiguous, the compartmentalization of the ER into sub-domain cannot exclusively be created by membrane barriers. Adapter proteins nucleate the formation of protein complexes to create sub-domains in the ER. Tetratricopeptide repeats (TPR) containing proteins are known to organize protein complexes involved in a wide range of cellular processes. While the human genome is predicted to encode ~ 180 TPR proteins, only two have previously been shown to localize to the ER. We hypothesized that there are additional TPR-containing adapter proteins that contribute to the organization or compartmentalization of ER processes. To this end, we screened an in silico library of putative TPR containing proteins from the Regan laboratory (Yale University) to identify proteins that potentially possess an N-terminal ER targeting signal sequence. This screen, combined with additional in silico approaches, identified nine putative ER proteins that contained between three to ten TPR motifs. While some of the identified proteins are soluble ER proteins (i.e. TTC13 and TTC17), others were found to reside in the ER membrane with their TPR domains facing the ER lumen (TMTC1-4). TMTC1 and TMTC2 were found to interact with the ER calcium pump SERCA2B, and TMTC2 with calnexin. Additionally, live cell calcium measurements showed a role for TMTC1 and TMTC2 in calcium homeostasis. Overall, this strategy was successful in identifying novel ER proteins with TPR motifs, and this approach can be applied to identify proteins with specific motifs in the ER or other organelles.Molecular and Cellular BiologyDoctor of Philosophy (PhD

Skapandet av en generisk affärsmodell. En forskningssyntes av affärsmodellers komponenter & samband

Bakgrund och problem: Begreppet affärsmodell har under det senaste decenniet blivit mer och mer vanligt förekommande, både inom näringslivet och forskarsamhället. Dock råder det en begreppsförvirring kring vad som menas med en affärsmodell och vad modellen skall innehålla. Detta har resulterat i felaktig användning både hos teoretiker och professionella aktörer. Syfte: Att genomföra en litteraturgranskning i syfte att tydliggöra befintliga affärsmodeller samt att utifrån en analys av dessas komponenter och sammanlänkningar skapa en generisk affärsmodell. Avgränsningar: Uppsatsens ämnar söka en generisk affärsmodell som tar sin utgångspunkt i det konceptuella stadiet. Därför kommer inte implementering eller applicering av affärsmodeller samt deras förändring att beröras. Metod: Metoden som använts kallas litteraturgranskning. Syftet med en litteraturgranskning är att skapa översikt inom ett forskningsområde där det saknas samt att söka praktisk tillämpning av tidigare presenterat material. Slutsatser: En konceptuell generisk affärsmodell med komponenter och samband har skapats. En affärsmodell som syftar till att hjälpa företag att organisera sin verksamhet för att nå ett effektivare resursutnyttjande och tolka sin omvärld har framställts. Förslag till fortsatt forskning: En komparativ studie av den framtagna generiska affärsmodellen utifrån en implementeringsanalys på ett antal företag. Att undersöka om näringslivet har befintliga affärsmodeller ej presenterade i vetenskaplig text som kan bidra med nya tankar eller idéer. Att utvärdera affärsmodeller från ett immaterialrättsligt perspektiv, samt studera dessa ev. konsekvenser för svenska företag

EDEM1 recognition and delivery of misfolded proteins to the SEL1L-containing ERAD complex

Terminally misfolded or unassembled secretory proteins are retained in the endoplasmic reticulum (ER) and subsequently cleared by the ER-associated degradation (ERAD) pathway. The degradation of ERAD substrates involves mannose trimming of N-linked glycans; however, the mechanisms of substrate recognition and sorting to the ERAD pathway are poorly defined. EDEM1 (ER degradation-enhancing alpha-mannosidase-like 1 protein) has been proposed to play a role in ERAD substrate signaling or recognition. We show that EDEM1 specifically binds nonnative proteins in a glycan-independent manner. Inhibition of mannosidase activity with kifunensine or disruption of the EDEM1 mannosidase-like domain by mutation had no effect on EDEM1 substrate binding but diminished its association with the ER membrane adaptor protein SEL1L. These results support a model whereby EDEM1 binds nonnative proteins and uses its mannosidase-like domain to target aberrant proteins to the ER membrane dislocation and ubiquitination complex containing SEL1L