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A Conserved C‐terminal Region of Gα12 and Gα13 Harbors Unique Determinants of SRF Signaling and RhoGEF Binding
Author(s) -
Mull Makenzy L.,
Fleming Todd L.,
Quick Courtney R.,
Meigs Thomas E.
Publication year - 2019
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.2019.33.1_supplement.477.7
Subject(s) - heterotrimeric g protein , serum response factor , biology , subfamily , signal transduction , microbiology and biotechnology , conserved sequence , peptide sequence , g protein , transcription factor , biochemistry , gene
Heterotrimeric G proteins of the G12/13 subfamily play key signaling roles in cell growth, oncogenic transformation, migration, and invasion. The G protein alpha subunits, Gα12 and Gα13, share 67% amino acid identity and several downstream signaling pathways, including transcriptional activation via Serum Response Factor (SRF). Gα12 and Gα13 have multiple, unique binding partners, suggesting divergent signaling mechanisms within this subfamily. To identify different structural features required for growth signaling in Gα12 and Gα13, we utilized amino acid substitutions from non‐SRF signaling invertebrate homologs. Replacing the N‐terminal region of these mammalian α subunits with invertebrate sequence caused no disruption of SRF signaling. Conversely, invertebrate substitution of a highly conserved sequence downstream of the Switch III region abolished SRF signaling by Gα12 and Gα13. In this “Post‐Switch region” of Gα12, a single amino acid substitution disrupted its SRF signaling, while the same mutation in Gα13 had no effect. Replacement of additional residues in this region uncoupled Gα13 from SRF activation, suggesting divergent growth signaling mechanisms in the G12/13 subfamily. In addition, invertebrate substitution in the Post‐Switch region disrupted Gα13 interaction with RhoGEFs, whereas the corresponding SRF‐uncoupled Gα12 retained binding to these effector proteins. To further explore differences in the growth signaling mechanisms of Gα12 and Gα13, we engineered invertebrate chimeras within the C‐terminal α5 helix. These substitutions partially disrupted Gα12‐mediated SRF signaling but were inconsequential for Gα13. Our findings reveal novel C‐terminal motifs in Gα12 and Gα13 that are necessary for their non‐overlapping mechanisms of RhoGEF binding and SRF‐mediated cell growth. Support or Funding Information We acknowledge support from the North Carolina GlaxoSmithKline Foundation, the C.D. Spangler Foundation, and the UNC Lineberger Comprehensive Cancer Center. This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .