Functional characterization of Rho GTPase activating proteins SYDE1 and SYDE2
- 1Yale University School of Medicine
Abstract
The human genome encodes more than 60 proteins containing Rho GTPase activating protein (RhoGAP) domains, many of which remain understudied with respect to their target specificity and biological roles. SYDE1 and SYDE2 are two such orphan RhoGAPs, for which there are few studies characterizing their biochemical and cellular functions and conflicting reports identifying their cognate GTPases. We previously identified SYDE1 and SYDE2 in a screen for substrates of the c-Jun N-terminal kinases. Here, we show that SYDE1 and SYDE2 are preferentially phosphorylated by JNK1 relative to other mitogen-activated protein kinases (MAPKs) at sites proximal to a kinase docking region. Purified SYDE1 and SYDE2 are shown to have significant catalytic GAP activity toward RhoA, Rac1, and Cdc42. However, neither up- nor down-regulation of SYDE1/2 expression leads to detectable changes in bulk GTP loading of any of these GTPases. Nevertheless, we demonstrate that SYDE1 and SYDE2, in a partially GAP-dependent manner, increase cell spreading and number of focal adhesions, and promote more directionally persistent migration in HEK293 cells. Together, these findings establish SYDE1 and SYDE2 as robust JNK substrates with catalytic activity toward a set of Rho GTPases and reveal basic functions of SYDE1 and SYDE2 in regulating cell morphology, adhesion, and migration.
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BibTeX
@misc{song2026functional,
title = {{Functional characterization of Rho GTPase activating proteins SYDE1 and SYDE2}},
author = {C. Song and S. An and H. J. Lou and B. E. Turk},
howpublished = {bioRxiv},
year = {2026},
month = aug,
doi = {10.64898/2026.08.31.748432},
url = {https://www.biorxiv.org/content/10.64898/2026.08.31.748432v1},
note = {CC BY-NC-ND},
}
RIS
TY - UNPB
TI - Functional characterization of Rho GTPase activating proteins SYDE1 and SYDE2
AU - C. Song
AU - S. An
AU - H. J. Lou
AU - B. E. Turk
PY - 2026
DA - 2026/08/31
PB - bioRxiv
DO - 10.64898/2026.08.31.748432
UR - https://www.biorxiv.org/content/10.64898/2026.08.31.748432v1
AB - The human genome encodes more than 60 proteins containing Rho GTPase activating protein (RhoGAP) domains, many of which remain understudied with respect to their target specificity and biological roles. SYDE1 and SYDE2 are two such orphan RhoGAPs, for which there are few studies characterizing their biochemical and cellular functions and conflicting reports identifying their cognate GTPases. We previously identified SYDE1 and SYDE2 in a screen for substrates of the c-Jun N-terminal kinases. Here, we show that SYDE1 and SYDE2 are preferentially phosphorylated by JNK1 relative to other mitogen-activated protein kinases (MAPKs) at sites proximal to a kinase docking region. Purified SYDE1 and SYDE2 are shown to have significant catalytic GAP activity toward RhoA, Rac1, and Cdc42. However, neither up- nor down-regulation of SYDE1/2 expression leads to detectable changes in bulk GTP loading of any of these GTPases. Nevertheless, we demonstrate that SYDE1 and SYDE2, in a partially GAP-dependent manner, increase cell spreading and number of focal adhesions, and promote more directionally persistent migration in HEK293 cells. Together, these findings establish SYDE1 and SYDE2 as robust JNK substrates with catalytic activity toward a set of Rho GTPases and reveal basic functions of SYDE1 and SYDE2 in regulating cell morphology, adhesion, and migration.
ER -