Poster Annual Conference of the Genetics Society of Australasia with the NZ Society for Biochemistry & Molecular Biology

Structural investigation of the Hsc70 heat shock cognate protein for applications in radiotherapy (776)

Jamin L.B Martin 1 2 , Sigurd M Wilbanks 2
  1. Radiation Oncology, Southern District Health Board, Dunedin, New Zealand
  2. Department of Biochemistry, University of Otago, Dunedin, New Zealand

Hsp70s are a ubiquitous family of molecular chaperones and heatshock (or stress response) proteins. Expression of Hsp70 family members has been shown to be induced in many tumour types. This overexpression is likely driven by the stresses of the tumour microenvironment. Hsp70 expression of can be stimulated by the stresses in the tumour cell environment, including pH and loss of proteostasis. In addition, survival in the tumour environment exerts selective pressure on hypoxic cells for increased expression of Hsp70s, including that owing to mutation and genetic rearrangement. This overexpression of Hsp70s contributes to tumour cells being able to thrive in their microenvironment, bypassing limits on their growth and induction of apoptosis. Its increased presence in hypoxic cells confers resilience to damage of radiation therapy, perhaps by contributing to the low biological effectiveness of photons (x-rays). Therefore, pharmacological inhibitors of Hsp70s could potentially increase the effectiveness of conventional radiotherapy, as well as decreasing the risk of resurgent hypoxic cells post treatment. This work is aimed at an x-ray crystal structure of the ATP-bound form of Hsc70, the most abundant, constitutively expressed human Hsp70. It uses variants containing a crosslink in order to stabilize the C-terminal substrate binding domain, increasing the likelihood and quality of protein crystals. Elucidation of the ATP-bound structure of Hsc70 and description of its active site will facilitate inhibitor design. Two crosslinkable variants have been designed and expressed in Escherichia coli with sufficient yield and solubility. Crystallization trials will follow purification and oxidative crosslinking.