The recent public releases of AI tools such as ChatGPT have forced computer science educators to reconsider how they teach. These tools have demonstrated considerable ability to generate code and answer conceptual questions, rendering them incredibly useful for completing CS coursework. While overreliance on AI tools could hinder students' learning, we believe they have the potential to be a helpful resource for both students and instructors alike. We propose a novel system for instructor-mediated GPT interaction in a class discussion board. By automatically generating draft responses to student forum posts, GPT can help Teaching Assistants (TAs) respond to student questions in a more timely manner, giving students an avenue to receive fast, quality feedback on their solutions without turning to ChatGPT directly. Additionally, since they are involved in the process, instructors can ensure that the information students receive is accurate, and can provide students with incremental hints that encourage them to engage critically with the material, rather than just copying an AI-generated snippet of code. We utilize Piazza-a popular educational forum where TAs help students via text exchanges-as a venue for GPT-assisted TA responses to student questions. These student questions are sent to GPT-4 alongside assignment instructions and a customizable prompt, both of which are stored in editable instructor-only Piazza posts. We demonstrate an initial implementation of this system, and provide examples of student questions that highlight its benefits.