TBK1 and cancer: Meanwhile, phosphorylation of S177 and S513 promotes recruitment and retention of OPTN/TBK1 on ubiquitinated, damaged mitochondria.161 Moreover, TBK1 can also phosphorylate OPTN at S177 site, which helps to enhance LC3 binding affinity and autophagic clearance of cytosolic salmonella.162 p85β, encoded by PI3KR2, is the p85 regulatory subunit of PI3K and is frequently amplified in cancers.