Albany 2019: 20th Conversation - Abstracts

category image Albany 2019
Conversation 20
June 11-15 2019
Adenine Press (2019)

The Structural and quantitative study of the destruction complex in the canonical Wnt-signaling pathway

The canonical Wnt/β-catenin signaling pathway plays pivotal roles in tumorigenesis. The cytosolic level of β-catenin is mainly regulated by a postulated molecular machine, which is called the β-catenin destruction complex. However, while the term molecular machine usually connotes a discrete multiprotein complex like the ribosome, this machine, while strongly supported indirectly has never been purified or seen. The destruction complex may be transient, and its postulated stoichiometry may never be realized at any given instant. The instability of the components may lead to many different kinetically determined structures. The variable stoichiometry could also be very relevant physiologically. This complex contains a large scaffold, the adenomatous polyposis coli protein (APC), which acts as an important tumor suppressor and has been well characterized in colorectal cancer. APC mutants in nearly all colorectal cancer have variable truncations, which could produce different subunit configurations between APC and β-catenin, influencing the degradation of β-catenin downstream. To study the dynamic stoichiometry, we are developing a quantitative single-molecule assay in the cell extracts of both normal cells and colorectal cancer cells to observe the assembly process with millisecond time resolution. Ultimately combining this kinetic information with biochemical crosslinking and cryo-electron microscopy, we hope to capture the transient state of the destruction complex of kinetically stable subcomplexes. The purpose of the project is to illustrate the dynamic process of the destruction complex by combining structural information and quantitative single-molecule data, aiming to find the essential role of APC in colorectal cancer.

Bai Luan
Wenzhe Ma
Hong Kang
Ying Lu
Marc W. Kirschner

Department of Systems Biology
Harvard Medical School
200 Longwood Ave
Boston, MA 02115