Novel Role of Phosphorylation-Dependent Interaction between FtsZ and FipA in Mycobacterial Cell Division

Abstract

<div><p>The bacterial divisome is a multiprotein complex. Specific protein-protein interactions specify whether cell division occurs optimally, or whether division is arrested. Little is known about these protein-protein interactions and their regulation in mycobacteria. We have investigated the interrelationship between the products of the <em>Mycobacterium tuberculosis</em> gene cluster <em>Rv0014c-Rv0019c</em>, namely PknA (encoded by <em>Rv0014c</em>) and <u>F</u>tsZ-<u>i</u>nteracting <u>p</u>rotein A, FipA (encoded by <em>Rv0019c</em>) and the products of the division cell wall (<em>dcw</em>) cluster, namely FtsZ and FtsQ. <em>M. smegmatis</em> strains depleted in components of the two gene clusters have been complemented with orthologs of the respective genes of <em>M. tuberculosis</em>. Here we identify FipA as an interacting partner of FtsZ and FtsQ and establish that PknA-dependent phosphorylation of FipA on T77 and FtsZ on T343 is required for cell division under oxidative stress. A <em>fipA</em> knockout strain of <em>M. smegmatis</em> is less capable of withstanding oxidative stress than the wild type and showed elongation of cells due to a defect in septum formation. Localization of FtsQ, FtsZ and FipA at mid-cell was also compromised. Growth and survival defects under oxidative stress could be functionally complemented by <em>fipA</em> of <em>M. tuberculosis</em> but not its T77A mutant. Merodiploid strains of <em>M. smegmatis</em> expressing the FtsZ(T343A) showed inhibition of FtsZ-FipA interaction and Z ring formation under oxidative stress. Knockdown of FipA led to elongation of <em>M. tuberculosis</em> cells grown in macrophages and reduced intramacrophage growth. These data reveal a novel role of phosphorylation-dependent protein-protein interactions involving FipA, in the sustenance of mycobacterial cell division under oxidative stress.</p></div>