BMBDG Seminar - Lawrence Kazak

“Adipocyte Control of Energy Balance” by Lawrence Kazak, Assistant Professor, Department of Biochemistry, McGill University, Rosalind and Morris Goodman Cancer Research Centre

The obesity pandemic has precipitated a steep rise in metabolic diseases such as type 2 diabetes, heart disease, and many cancers. Globally, 40% of adults are overweight and 15% are obese. Obesity occurs when energy intake exceeds energy expenditure (energy imbalance). Thus, obesity can be caused by increased energy intake, decreased energy expenditure, or a combination of the two. Adipose tissue plays a central role in regulating whole-body energy homeostasis. Specifically, thermogenic (brown and beige) adipocytes can catabolize stored energy to generate heat. This capacity for thermogenesis holds tremendous promise as a therapy for metabolic diseases. The major focus of my lab is to identify the molecular mechanisms that drive adipocyte thermogenesis. By elucidating the genetic and metabolic pathways that control thermogenesis, we aim to recapitulate the positive effects of brown fat energy expenditure on health. To accomplish this, my lab uses molecular biology, bioenergetics, and stable isotope tracing to understand how adipocytes dissipate energy, at the level of cells and organelles. The physiological relevance of our findings is then examined using mice with engineered mutations in putative energy consuming pathways to test if these animals become obese (or not) when exposed to high calorie foods. Our research program will inform the development of therapies that support energy expenditure to combat obesity and related metabolic disorders.

Monday, April 8, 2019 @3:00 pm, LSC#3, 2350 Health Sciences Mall.

Host: Dr. Christian Kastrup

“Characterizing the assembly and molecular interactions of the fission yeast Atg1 autophagy regulatory complex”,  by Tamiza Nanji, PhD Candidate, Yip Lab.

Abstract: Macroautophagy, often referred to as autophagy, is a non-selective degradation mechanism used by eukaryotic cells to recycle cytoplasmic material and maintain homeostasis. Upregulated under starvation to generate molecular building blocks for ongoing cellular processes, this pathway requires the coordinated action of six multi-protein complexes, the Atg1/ULK1 complex being the first. Although, the Atg1 complex has been extensively studied in Saccharomyces cerevisiae, far less is known about the biochemical and structural properties of its mammalian counterpart, the ULK1 complex. Unlike the S. cerevisiae Atg1 complex which contains five subunits (Atg1, Atg13, Atg17, Atg29, and Atg31), the ULK1 complex consists of four proteins (ULK1, FIP200/RB1CC1, ATG13, and ATG101) that are technically more challenging to study. In this study, I characterized the Atg1 complex from fission yeast, Schizosaccharomyces pombe, as the composition of proteins resembles the mammalian ULK1 complex but is more amenable to biochemical analyses. The Atg1 complex in S. pombe is composed of Atg1 (ULK1 counterpart), Atg13, Atg17 (FIP200 counterpart) and Atg101. We found that the interactions between Atg1, Atg17, and Atg13 are conserved while Atg101 does not replace Atg29 and Atg31. Instead, Atg101 binds to Atg1 and the HORMA domain of Atg13. Furthermore, Atg101 was previously shown to contain a conserved loop, termed the WF finger, postulated to bind and recruit downstream autophagy-related proteins and effectors. Using affinity purification mass spectrometry, we further investigated the potential interacting partners of S. pombe Atg101 under autophagy-inducing and non-inducing conditions. We obtained 625 proteins that co-purified with Atg101-GFP from cells grown in defined media. We used in vitro pairwise studies to confirm the interaction between Atg101 and prey proteins. 9 of the 16 proteins tested were confirmed including Fkh1, an FKBP-type peptidyl-prolyl cis-trans isomerase. We further explored the interaction interface between Atg101 and Fkh1 and found that the WF finger is required for the interaction in vitro. Although the S. cerevisiae Fkh1 homologue, FKBP12, interacts with rapamycin; Fkh1 it is not thought to be directly involved in autophagy. Collectively, our results give new insights into an Atg101-containing Atg1/ULK1 complex and reveals that Atg101’s function may span beyond autophagy.

Host: Calvin Yip
Monday, March 18, 2019 at 3:00 pm. LSC#3, 2350 Health Sciences Mall.

“Characterizing the assembly and molecular interactions of the fission yeast Atg1 autophagy regulatory complex,” by Tamiza Nanji, Candidate Yip Lab.

Abstract:

Macroautophagy, often referred to as autophagy, is a non-selective degradation mechanism used by eukaryotic cells to recycle cytoplasmic material and maintain homeostasis. Upregulated under starvation to generate molecular building blocks for ongoing cellular processes, this pathway requires the coordinated action of six multi-protein complexes, the Atg1/ULK1 complex being the first. Although, the Atg1 complex has been extensively studied in Saccharomyces cerevisiae, far less is known about the biochemical and structural properties of its mammalian counterpart, the ULK1 complex. Unlike the S. cerevisiae Atg1 complex which contains five subunits (Atg1, Atg13, Atg17, Atg29, and Atg31), the ULK1 complex consists of four proteins (ULK1, FIP200/RB1CC1, ATG13, and ATG101) that are technically more challenging to study. In this study, I characterized the Atg1 complex from fission yeast, Schizosaccharomyces pombe, as the composition of proteins resembles the mammalian ULK1 complex but is more amenable to biochemical analyses. The Atg1 complex in S. pombe is composed of Atg1 (ULK1 counterpart), Atg13, Atg17 (FIP200 counterpart) and Atg101. We found that the interactions between Atg1, Atg17, and Atg13 are conserved while Atg101 does not replace Atg29 and Atg31. Instead, Atg101 binds to Atg1 and the HORMA domain of Atg13. Furthermore, Atg101 was previously shown to contain a conserved loop, termed the WF finger, postulated to bind and recruit downstream autophagy-related proteins and effectors. Using affinity purification mass spectrometry, we further investigated the potential interacting partners of S. pombe Atg101 under autophagy-inducing and non-inducing conditions. We obtained 625 proteins that co-purified with Atg101-GFP from cells grown in defined media. We used in vitro pairwise studies to confirm the interaction between Atg101 and prey proteins. 9 of the 16 proteins tested were confirmed including Fkh1, an FKBP-type peptidyl-prolyl cis-trans isomerase. We further explored the interaction interface between Atg101 and Fkh1 and found that the WF finger is required for the interaction in vitro. Although the S. cerevisiae Fkh1 homologue, FKBP12, interacts with rapamycin; Fkh1 it is not thought to be directly involved in autophagy. Collectively, our results give new insights into an Atg101-containing Atg1/ULK1 complex and reveals that Atg101’s function may span beyond autophagy.

Thursday, March 28, 2019 at 9:00 am in Room 203, Graduate Student Centre, 6371 Crescent Road.

“The Roles of Fibrinolysis in Regulating Coagulation Factor XIII,” by Steve Hur, Candidate in Kastrup Lab.

Abstract:

Coagulation factor XIII (FXIII) is a protransglutaminase enzyme that is activated at the end of the coagulation cascade. Activated FXIII (FXIIIa) stabilizes the blood clot from premature lysis by covalently crosslinking fibrin molecules to itself and to other anti-fibrinolytic proteins. Although the role of FXIIIa as an antifibrinolytic protein has been well characterized, the role of fibrinolysis in regulating FXIII and FXIIIa has not been characterized. We showed that plasmin preferentially cleaves the active enzyme FXIIIa, but not the zymogen FXIII, during clot lysis, but not during clot formation. During catheter directed thrombolysis, where plasmin levels are highly increased, FXIII and FXIIIa levels were substantially decreased in some patients. We identified a novel substrate of FXIIIa: amyloid beta (Aβ). FXIIIa covalently crosslinked Aβ40 into dimers and oligomers, as well as to fibrin, and to blood clots.

Friday, January 25, 2019 at 12:30 pm, Room 200, Graduate Student Centre, 6371 Crescent Road.