Serine-threonine kinase ROCK2 regulates germinal center B cell positioning and cholesterol biosynthesis

• Published in: The Journal of clinical investigation 2020-07, Vol.130 (7), p.3654-3670
• Main Authors: Ricker, Edd, Chinenov, Yurii, Pannellini, Tania, Flores-Castro, Danny, Ye, Chao, Gupta, Sanjay, Manni, Michela, Liao, James K, Pernis, Alessandra B
• Format: Article
• Language: English
• Subjects: AKT protein; Analysis; Animals; B cells; B-Lymphocytes - cytology; B-Lymphocytes - metabolism; Biomedical research; Biosynthesis; CD40 antigen; Cell differentiation; Cell Line; Cholesterol; Cholesterol - biosynthesis; Cholesterol - genetics; Chromatin; Enzymes; Forkhead Box Protein O1 - genetics; Forkhead Box Protein O1 - metabolism; FOXO1 protein; G proteins; Germinal Center - cytology; Germinal Center - metabolism; Germinal centers; Interferon; Interferon regulatory factor; Interferon Regulatory Factors - genetics; Interferon Regulatory Factors - metabolism; Interleukin 21; Kinases; Lymphocytes; Lymphocytes B; Lymphocytes T; Metabolism; Mice; Mice, Transgenic; Next-generation sequencing; Phosphorylation; Physiological aspects; Protein kinase; Protein-serine/threonine kinase; Proto-Oncogene Proteins c-akt - genetics; Proto-Oncogene Proteins c-akt - metabolism; Regulation; Regulatory sequences; rho-Associated Kinases - genetics; rho-Associated Kinases - metabolism; RhoA protein; Ribonucleic acid; RNA; RNA sequencing; Serine; Statins; Sterol Regulatory Element Binding Protein 2 - genetics; Sterol Regulatory Element Binding Protein 2 - metabolism; Sterols; T cells; Transcription factors; Transposase
• ISSN: 0021-9738; 1558-8238
• DOI: 10.1172/jci132414

Germinal center (GC) responses require B cells to respond to a dynamic set of intercellular and microenvironmental signals that instruct B cell positioning, differentiation, and metabolic reprogramming. RHO-associated coiled-coil-containing protein kinase 2 (ROCK2), a serine-threonine kinase that can be therapeutically targeted by ROCK inhibitors or statins, is a key downstream effector of RHOA GTPases. Although RHOA-mediated pathways are emerging as critical regulators of GC responses, the role of ROCK2 in B cells is unknown. Here, we found that ROCK2 was activated in response to key T cell signals like CD40 and IL-21 and that it regulated GC formation and maintenance. RNA-Seq analyses revealed that ROCK2 controlled a unique transcriptional program in GC B cells that promoted optimal GC polarization and cholesterol biosynthesis. ROCK2 regulated this program by restraining AKT activation and subsequently enhancing FOXO1 activity. ATAC-Seq (assay for transposase-accessible chromatin with high-throughput sequencing) and biochemical analyses revealed that the effects of ROCK2 on cholesterol biosynthesis were instead mediated via a novel mechanism. ROCK2 directly phosphorylated interferon regulatory factor 8 (IRF8), a crucial mediator of GC responses, and promoted its interaction with sterol regulatory element-binding transcription factor 2 (SREBP2) at key regulatory regions controlling the expression of cholesterol biosynthetic enzymes, resulting in optimal recruitment of SREBP2 at these sites. These findings thus uncover ROCK2 as a multifaceted and therapeutically targetable regulator of GC responses.