Lsc is required for marginal zone B cells, regulation of lymphocyte motility and immune responses


Lsc (the murine homolog of human p115 Rho GEF) is a member of the Dbl-homology family of GTP exchange factors and is a specific activator of Rho. Lsc is activated by the Gα13 subunit of heterotrimeric G proteins and contains a regulator of G protein signaling domain that downmodulates Gα12 and Gα13. Lsc is expressed primarily in the hematopoietic system and links the activation of Gα12 and Gα13–coupled receptors to actin polymerization in B and T cells. Lsc is essential for marginal zone B (MZB) cell homeostasis and for the generation of immune responses. Although Lsc-deficient lymphocytes show reduced basal motility, MZB cells show enhanced migration after serum activation. Thus, Lsc is a critical regulator of MZB cells and immune functions.

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Figure 1: Lsc expression is specific to the hematopoietic system.
Figure 2: Requirement for Lsc in responses to agonists implicated in activation of Gα12 and Gα13.
Figure 3: Analysis of B cell populations in Lsc−/− mice.
Figure 4: MZB cell defect in Lsc−/− mice is cell autonomous.
Figure 5: Defective humoral responses in Lsc−/− mice.
Figure 6: Lymphocyte proliferation in the absence of Lsc.
Figure 7: Altered migration of Lsc−/− lymphocytes.


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We thank T. Wirth and L. Nitschke for critical reading of the manuscript; M. Zimmer for assistance with the mapping of Lsc genomic sequences; and M. Eigenthaler and U. Walter for advice on platelet analysis. Supported by Marie Curie (K. M.) and grants from SFB 465, DFG (Fi2-2) and the state of Baden-Württemberg (K.-D. F.).

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Correspondence to Klaus-Dieter Fischer.

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Web Figure 1.

Disruption of the gene that encodes Lsc. (a) Integration of the Lsc targeting vector in the genomic locus. Exons are represented by black boxes. The neo cassette was cloned in reverse orientation into two exons of the DH domain, replacing a PvuI-XbaI segment. Locations of primers used for PCR are indicated with triangles. Probes A and B were used for Southern blot detection of long and short arms, respectively. B, BamHI; H, HindIII; S, SacI; E, EcoRI; P, PvuI; Xh, XhoI. (b) Southern blot analysis. Genomic DNA from Lsc+/+, Lsc-/- and Lsc+/- mice was digested with BamHI and hybridized with probes A and B. (c) PCR analysis of tail DNA from Lsc+/+, Lsc+/- and Lsc-/- mice. (d) Immunoblot analysis of total spleen cell lysates. Lsc expression was detected with anti-Lsc. (e) Intracellular stain of Lsc in CD4+ lymph node cells from Lsc+/+, Lsc+/- and Lsc-/- mice. Isotype control is shown as a dotted line. (GIF 36 kb)

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Girkontaite, I., Missy, K., Sakk, V. et al. Lsc is required for marginal zone B cells, regulation of lymphocyte motility and immune responses. Nat Immunol 2, 855–862 (2001).

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