Access Type

Open Access Thesis

Date of Award

January 2017

Degree Type

Thesis

Degree Name

M.S.

Department

Pharmaceutical Sciences

First Advisor

Zhengping Yi

Abstract

Protein Phosphatase 2A (PP2A), a major serine/threonine phosphatase involved in insulin signaling pathway, plays a critical role in the development of insulin resistance and type 2 diabetes (T2D), which is characterized with hyperinsulinemic hyperglycemic condition. Moreover, majority of the glucose disposal takes place in the skeletal muscle which is also the main tissue responsible for insulin resistance. The catalytic subunit of PP2A (PP2Ac) can interact with multiple regulatory subunits and other regulatory proteins as well as substrates. These interactions are important for maintain normal PP2A function and subsequent cell signaling. We hypothesized that hyperinsulinemic hyperglycemic condition and insulin stimulation would result in differentially changed protein-protein interactions involving PP2Ac in primary human skeletal muscle cells derived from lean healthy participants.

Using UPLC-nanoESI-MS/MS, 202 PP2Ac interaction partners were identified in primary human skeletal muscle cells from 8 lean heathy participants. Out of which 18 partners were previously identified in the islet beta cells by our group. In addition, 19 interaction partners of PP2Ac showed a significant difference among 4 treatment groups: low glucose no insulin without acute 15-min insulin treatment (LGNI BAS), low glucose no insulin with acute 15-min insulin treatment (LGNI INS), high glucose high insulin without acute 15-min insulin stimulation (HGHI BAS) and high glucose high insulin with acute 15-min insulin stimulation (HGHI INS). Under basal conditions (i.e., without acute 15-minute insulin stimulation), 6 proteins showed a significant change in PP2Ac interaction between the low glucose no insulin and chronicle hyperinsulinemia and hyperglycemia conditions (LGNI BAS vs HGHI BAS, p<0.05). In addition, 2 proteins showed significant difference in PP2Ac interaction in LGNI condition in response to insulin stimulation (LGNI BAS vs LGNI INS, p<0.05). In HGHI conditions, 4 proteins showed significant difference in PP2Ac interaction in response to insulin stimulation (HGHI Bas vs HGHI INS, p<0.05). Upon acute insulin stimulation, 11 proteins showed significant difference in PP2Ac interaction in HGHI condition when compared to the LGNI condition (LGNI INS vs HGHI INS, p<0.05). These differential changes of PP2Ac interaction partners among the 4 treatments provide new information regarding PP2A in primary human skeletal muscle cells under hyperinsulinemic hyperglycemic conditions.

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