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Mechanism and Function of the Supercomplex KARATE in Insulin Signaling

Award Number: R01DK129699
ORGANIZATION: NATIONAL INSTITUTE OF DIABETES & DIGESTIVE & KIDNEY DISEASES
OPDIV: NIH
AWARD CLASS: DISCRETIONARY
AWARD ACTIVITY TYPE: SCIENTIFIC/HEALTH RESEARCH (INCLUDES SURVEYS)
PERIOD OF PERFORMANCE START DATE: 04/05/2022
PERIOD OF PERFORMANCE END DATE: 01/31/2026

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Mechanism and Function of the Supercomplex KARATE in Insulin Signaling - Abstract AKT is one of the most important protein kinases in insulin signaling. In response to insulin, AKT becomes active and phosphorylates critical metabolic effectors, including TBC1D4, GSK3, TSC2, and FOXO. These proteins regulate glucose uptake through the translocation of the glucose transporter GLUT4 to the plasma membrane, glycogen synthesis, lipid and protein synthesis, and glucose production in adipose tissues, skeletal muscles, and livers. Abnormalities in AKT activation have been linked to insulin resistance in type 2 diabetes. AKT is activated by two other protein kinases, mTORC2 and PDK1. mTORC2 phosphorylates the hydrophobic motif of AKT and opens the catalytic domain. PDK1 then phosphorylates AKT to activate its enzymatic activity. The activation step by PDK1 is controlled by the recruitment of AKT and PDK1 to the plasma membrane. However, understanding of how mTORC2 is regulated to phosphorylate AKT is limited. To fill this critical knowledge gap, this grant application tests the hypothesis that KRAS4B, RHOA, and mTORC2 form a supercomplex (termed KARATE) to direct the enzymatic activity of mTORC2 toward AKT in insulin signaling. Toward this goal, we will identify the mechanism, localization, and regulation of the KARATE assembly. We will also determine the physiological function of KARATE in glucose homeostasis. We will employ multiple innovative tools, including: 1) our recently developed total biochemical reconstitution system for KARATE- mediated AKT phosphorylation; 2) a Dictyostelium bioreactor that enables the purification to functional human proteins to high homogeneity with critical post-translational modification; 3) our novel KARATE peptide inhibitor for in vitro and cellular studies; 4) our CRISPR-generated knockout cell lines for RHOA, KRAS and mTORC2 subunits; and 5) tissue-specific RHOA-knockout mice and phospho-defective RHOA mice. We anticipate that the successful completion of the work will significantly advance our understanding of insulin signaling and establish a solid foundation for future studies. Ultimately, this will help translate the fundamental biology of AKT signaling into medical treatments focused on KARATE for metabolic syndrome.


Issue Date FY	Funding FY	Legal Entity Name	Legal Entity Address	Legal Entity City	Legal Entity State	Legal Entity Zip Code	Legal Entity COUNTY	Legal Entity COUNTRY	Assistance Listing	Award Code	Budget Year	Action Date	Action Type	Action Amount

Issue Date FY: 2025 ( Subtotal = $437,172 )
2025	2025	THE JOHNS HOPKINS UNIVERSITY	3400 N CHARLES ST	BALTIMORE	MD	21218	BALTIMORE CITY	USA	Diabetes, Digestive, and Kidney Diseases Extramural Research	001	4	5/14/2025	NON-COMPETING CONTINUATION	$43,717
2025	2025	THE JOHNS HOPKINS UNIVERSITY	3400 N CHARLES ST	BALTIMORE	MD	21218	BALTIMORE CITY	USA	Diabetes, Digestive, and Kidney Diseases Extramural Research	000	4	2/17/2025	NON-COMPETING CONTINUATION	$393,455
														Subtotal = $437,172

Issue Date FY: 2024 ( Subtotal = $419,685 )
2024	2024	THE JOHNS HOPKINS UNIVERSITY	3400 N CHARLES ST	BALTIMORE	MD	21218	BALTIMORE CITY	USA	Diabetes, Digestive, and Kidney Diseases Extramural Research	001	3	5/7/2024	NON-COMPETING CONTINUATION	$26,230
2024	2024	THE JOHNS HOPKINS UNIVERSITY	3400 N CHARLES ST	BALTIMORE	MD	21218	BALTIMORE CITY	USA	Diabetes, Digestive, and Kidney Diseases Extramural Research	000	3	1/23/2024	NON-COMPETING CONTINUATION	$393,455
														Subtotal = $419,685

Issue Date FY: 2023 ( Subtotal = $437,172 )
2023	2023	JOHNS HOPKINS UNIVERSITY, THE	3400 N CHARLES ST	BALTIMORE	MD	21218	BALTIMORE CITY	USA	Diabetes, Digestive, and Kidney Diseases Extramural Research	000	2	1/20/2023	NON-COMPETING CONTINUATION	$437,172
														Subtotal = $437,172

Issue Date FY: 2022 ( Subtotal = $454,572 )
2022	2022	JOHNS HOPKINS UNIVERSITY, THE	3400 N CHARLES ST	BALTIMORE	MD	21218	BALTIMORE CITY	USA	Diabetes, Digestive, and Kidney Diseases Extramural Research	000	1	4/4/2022	NEW	$454,572
														Subtotal = $454,572

Grand Total All Awards = $1,748,601

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Mechanism and Function of the Supercomplex KARATE in Insulin Signaling

Award Number: R01DK129699

ORGANIZATION: NATIONAL INSTITUTE OF DIABETES & DIGESTIVE & KIDNEY DISEASES

OPDIV: NIH

AWARD CLASS: DISCRETIONARY

AWARD ACTIVITY TYPE: SCIENTIFIC/HEALTH RESEARCH (INCLUDES SURVEYS)

PERIOD OF PERFORMANCE START DATE: 04/05/2022

PERIOD OF PERFORMANCE END DATE: 01/31/2026

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