Rgs13 constrains early B cell responses and limits germinal center sizes

• Published in: PloS one 2013-03, Vol.8 (3), p.e60139-e60139
• Main Authors: Hwang, Il-Young, Hwang, Kyung-Sun, Park, Chung, Harrison, Kathleen A, Kehrl, John H
• Format: Article
• Language: English
• Subjects: Analysis; Animals; Antigens; B cells; B-Lymphocytes - immunology; Biology; Cell cycle; Cell division; Cell membranes; Cell Proliferation; Cell size; Chemokines; Class switching; Cyclic AMP response element-binding protein; Enzyme-Linked Immunosorbent Assay; Exons - genetics; Flow Cytometry; Gene expression; Genes; Germinal Center - metabolism; Germinal centers; Guanosine triphosphatases; Guanosinetriphosphatase; Immunization; Immunoblotting; Immunoglobulins; Immunohistochemistry; Immunology; Infectious diseases; Kinases; Laboratories; Ligands; Lymph nodes; Lymphatic system; Lymphocyte receptors; Lymphocytes; Lymphocytes B; Membranes; Memory cells; Mice; Mice, Inbred C57BL; Microscopy; Microscopy, Confocal; Mutation; Nuclei (cytology); Organs; Plasma cells; Proteins; Real-Time Polymerase Chain Reaction; Recombination; RGS Proteins - genetics; RGS Proteins - metabolism; Signaling; Somatic hypermutation; Transcription; Transcription (Genetics); Translocation
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0060139

Germinal centers (GCs) are microanatomic structures that develop in secondary lymphoid organs in response to antigenic stimulation. Within GCs B cells clonally expand and their immunoglobulin genes undergo class switch recombination and somatic hypermutation. Transcriptional profiling has identified a number of genes that are prominently expressed in GC B cells. Among them is Rgs13, which encodes an RGS protein with a dual function. Its canonical function is to accelerate the intrinsic GTPase activity of heterotrimeric G-protein α subunits at the plasma membrane, thereby limiting heterotrimeric G-protein signaling. A unique, non-canonical function of RGS13 occurs following translocation to the nucleus, where it represses CREB transcriptional activity. The functional role of RGS13 in GC B cells is unknown. To create a surrogate marker for Rgs13 expression and a loss of function mutation, we inserted a GFP coding region into the Rgs13 genomic locus. Following immunization GFP expression rapidly increased in activated B cells, persisted in GC B cells, but declined in newly generated memory B and plasma cells. Intravital microscopy of the inguinal lymph node (LN) of immunized mice revealed the rapid appearance of GFP(+) cells at LN interfollicular regions and along the T/B cell borders, and eventually within GCs. Analysis of WT, knock-in, and mixed chimeric mice indicated that RGS13 constrains extra-follicular plasma cell generation, GC size, and GC B cell numbers. Analysis of select cell cycle and GC specific genes disclosed an aberrant gene expression profile in the Rgs13 deficient GC B cells. These results indicate that RGS13, likely acting at cell membranes and in nuclei, helps coordinate key decision points during the expansion and differentiation of naive B cells.