Dissecting the regulation, structural dynamics, and physiological role of human Ninj1 activity during Mtb-induced cell death on a molecular scale.

ongoing

Mycobacterium tuberculosis (Mtb) causes tuberculosis a leading infectious killer worldwide. Mtb primarily infects macrophages, leading to the death of some of these cells via distinct regulated cell death (RCD) mechanisms. While apoptosis facilitates Mtb elimination, necrotic cell deaths, like pyroptosis, necroptosis, and ferroptosis may enhance bacterial replication and spread. Mtb effectors, including the type VII secretion system ESX-1 and the cell wall lipid PDIM, induce host membrane damage, inducing necrotic cell death. Notably, the host lab has shown that inhibiting all RCD pathways does not prevent Mtb-induced cell lysis. However, depleting Ninjurin-1 (Ninj1), a membrane protein vital for plasma membrane (PM) rupture during various RCD pathways, mitigates Mtb-induced necrosis. Ninj1 oligomerization appears to occur after initial PM integrity disruption, yet the precise mechanisms governing Ninj1 activation and its role in Mtb-induced cell lysis remain unclear. I hypothesize that Ninj1 plays a crucial role in Mtb-induced lysis and that Mtb exploits this process through effector-mediated PM permeabilization. To investigate how Ninj1 oligomerization influences cell fate and the inflammatory response, I will leverage my expertise in super-resolution microscopy of pore-forming proteins alongside the host lab’s skills in Mtb infection biology. First, I will identify PM chemical and physical changes during RCD that correlate with Ninj1 oligomerization to elucidate the activation mechanism. Next, I will analyze Ninj1 dynamics and the functional impact of its macromolecular structures using DNA-PAINT super-resolution microscopy and long-term single-molecule tracking. Finally, I will determine whether Mtb activates Ninj1 via effector-induced PM damage and quantify the impact of this activation on the inflammatory response. This project aims to provide groundbreaking insights into cellular responses to Mtb and molecular inflammation research.