Faculty Opinions recommendation of Tyrosine phosphorylation of the BRI1 receptor kinase emerges as a component of brassinosteroid signaling in Arabidopsis.

Brassinosteroids (BRs) are important plant growth hormones that regulate a wide range of plant growth and developmental processes. The BR signals are perceived by two cell surface-localized receptor kinases, Brassinosteroid-Insensitive1 (BRI1) and BRI1-Associated receptor Kinase (BAK1), and reach the nucleus through two master transcription factors, bri1-EMS suppressor1 (BES1) and Brassinazole-resistant1 (BZR1). The intracellular transmission of the BR signals from BRI1/BAK1 to BES1/BZR1 is inhibited by a constitutively active kinase Brassinosteroid-Insensitive2 (BIN2) that phosphorylates and negatively regulates BES1/BZR1. Since their initial discoveries, further studies have revealed a plethora of biochemical and cellular mechanisms that regulate their protein abundance, subcellular localizations, and signaling activities. In this review, we provide a critical analysis of the current literature concerning activation, inactivation, and other regulatory mechanisms of three key kinases of the BR signaling cascade, BRI1, BAK1, and BIN2, and discuss some unresolved controversies and outstanding questions that require further investigation.

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BRI1/BAK1, a Receptor Kinase Pair Mediating Brassinosteroid Signaling

Cell ◽

10.1016/s0092-8674(02)00814-0 ◽

2002 ◽

Vol 110 (2) ◽

pp. 203-212 ◽

Cited By ~ 613

Author(s):

Kyoung Hee Nam ◽

Jianming Li

Keyword(s):

Receptor Kinase ◽

Brassinosteroid Signaling

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The insulinomimetic agents H2O2 and vanadate stimulate tyrosine phosphorylation of potential target proteins for the insulin receptor kinase in intact cells

Biochemical Journal ◽

10.1042/bj2880631 ◽

1992 ◽

Vol 288 (2) ◽

pp. 631-635 ◽

Cited By ~ 48

Author(s):

D Heffetz ◽

W J Rutter ◽

Y Zick

Keyword(s):

Insulin Receptor ◽

Tyrosine Phosphorylation ◽

Cho Cells ◽

Receptor Gene ◽

Chinese Hamster ◽

Receptor Kinase ◽

Intact Cells ◽

Insulin Receptor Gene ◽

Protein Tyrosine ◽

Insulin Receptor Kinase

H2O2 and vanadate are known insulinomimetic agents. Together they induce insulin's bioeffects with a potency which exceeds that seen with insulin, vanadate or H2O2 alone. We have previously shown that a combination of H2O2 and vanadate, when added to intact cells, rapidly stimulates protein tyrosine phosphorylation, owing to the inhibitory effects of these agents on intracellular protein tyrosine phosphatases (PTPases). Employing Western blotting with anti-phosphotyrosine antibodies, we have now identified in Chinese-hamster ovary (CHO) cells transfected with a wild-type insulin-receptor gene (CHO.T cells) several proteins (e.g. pp180, 125, 100, 60 and 52) whose phosphotyrosine content is rapidly increased upon treatment of the cells with a combination of insulin and 3 mM-H2O2. Tyrosine phosphorylation of these and additional proteins was further potentiated when 100 microM-sodium orthovanadate was added together with H2O2. The effects of insulin, insulin/H2O2, and H2O2/vanadate on tyrosine phosphorylation were markedly decreased in CHO cells transfected with an insulin-receptor gene where the twin tyrosines 1162 and 1163 were replaced with phenylalanine (CHO.YF-3 cells). Similarly, most of these proteins failed to undergo enhanced tyrosine phosphorylation in parental CHO cells incubated in the presence of insulin or the insulinomimetic agents. Our findings suggest that inhibition of PTPase activity by H2O2/vanadate augments the autophosphorylation of tyrosines 1162 and 1163 of the insulin receptor kinase, leading to its activation in an insulin-independent manner. As a result, tyrosine phosphorylation of potential targets for this enzyme takes place. Failure of H2O2/vanadate to induce phosphorylation of these proteins in receptor mutants lacking these twin tyrosine residues supports this hypothesis.

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In vitro tyrosine phosphorylation studies on RAS proteins and calmodulin suggest that polylysine-like basic peptides or domains may be involved in interactions between insulin receptor kinase and its substrate.

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.86.19.7306 ◽

1989 ◽

Vol 86 (19) ◽

pp. 7306-7310 ◽

Cited By ~ 26

Author(s):

Y. Fujita-Yamaguchi ◽

S. Kathuria ◽

Q. Y. Xu ◽

J. M. McDonald ◽

H. Nakano ◽

...

Keyword(s):

Insulin Receptor ◽

Tyrosine Phosphorylation ◽

Receptor Kinase ◽

Ras Proteins ◽

Insulin Receptor Kinase ◽

Basic Peptides

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Mechanistic analysis of the SERK3 elongated allele defines a role for BIR ectodomains in brassinosteroid signaling

10.1101/257543 ◽

2018 ◽

Author(s):

Ulrich Hohmann ◽

Joël Nicolet ◽

Andrea Moretti ◽

Ludwig A. Hothorn ◽

Michael Hothorn

Keyword(s):

Receptor Activation ◽

Surface Patch ◽

Receptor Kinase ◽

Leucine Rich Repeat ◽

Negative Regulators ◽

Signaling Complex ◽

The Core ◽

Mechanistic Analysis ◽

Brassinosteroid Signaling

AbstractThe leucine-rich repeat receptor kinase (LRR-RK) BRI1 requires a shape-complementary SERK co-receptor for brassinosteroid sensing and receptor activation. Interface mutations that weaken the interaction between receptor and co-receptor in vitro reduce brassinosteroid signaling responses. The SERK3 elongated (elg) allele maps to the complex interface and shows enhanced brassinosteroid signaling, but surprisingly no tighter binding to the BRI1 ectodomain in vitro. Here, we report that rather than promoting the interaction with BRI1, the elg mutation disrupts the ability of the co-receptor to interact with the ectodomains of BIR receptor pseudokinases, negative regulators of LRR-RK signaling. A conserved lateral surface patch in BIR LRR domains is required for targeting SERK co-receptors and the elg allele maps to the core of the complex interface in a 1.25 Å BIR3 - SERK1 structure. Collectively, our structural, quantitative biochemical and genetic analyses suggest that brassinosteroid signaling complex formation is negatively regulated by BIR receptor ectodomains.

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