The adaptor protein Bam32 regulates Rac1 activation and actin remodeling through a phosphorylation-dependent mechanism.

The Journal of Biological Chemistry
Atef AllamAaron J Marshall

Abstract

The B cell adaptor molecule of 32 kDa (Bam32) is an adaptor that links the B cell antigen receptor (BCR) to ERK and JNK activation and ultimately to mitogenesis. After BCR cross-linking, Bam32 is recruited to the plasma membrane and accumulates within F-actin-rich membrane ruffles. Bam32 contains one Src homology 2 and one pleckstrin homology domain and is phosphorylated at a single site, tyrosine 139. To define the function of Bam32 in membrane-proximal signaling events, we established human B cell lines overexpressing wild-type or mutant Bam32 proteins. The basal level of F-actin increased in cells expressing wild-type or myristoylated Bam32 but decreased in cells expressing either an Src homology-2 or Tyr-139 Bam32 mutant. Overexpression of wild-type Bam32 also affected BCR-induced actin remodeling, which was visualized as increases in F-actin-rich membrane ruffles. In contrast, Bam32 mutants largely blocked the BCR-induced increase in cellular F-actin. The positive and negative effects of Bam32 variants on F-actin levels were closely mirrored by their effects on the activation of the GTPase Rac1, which is known to regulate actin remodeling in lymphocytes. Bam32-deficient DT40 B cells showed decreased Rac1 activation and a f...Continue Reading

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Citations

May 2, 2008·International Immunology·Connie L SommersLawrence E Samelson
Nov 17, 2009·Immunological Reviews·Ting-Ting ZhangAaron J Marshall
Sep 2, 2008·Immunological Reviews·Sabrina RichardsEdward A Clark
Jan 1, 2005·Immunology Letters·Atef Allam, Aaron J Marshall
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Apr 2, 2019·Frontiers in Immunology·Niels J M VerstegenS Marieke van Ham
Mar 7, 2021·International Journal of Molecular Sciences·Li HaoLixin Liu

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