Date of Award

2017

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Physiology

Abstract

Focal adhesion kinase related non-kinase (FRNK) is an endogenous inhibitor of focal adhesion kinase (FAK) that has traditionally been used to inhibit FAK signaling in a variety of experiments and is also an important endogenous regulator of FAK signaling. More recently, FRNK has been shown to be of increasing importance in some pathologic conditions. Despite the increasing importance of FRNK, the molecular mechanism by which it functions remains unclear. In addition, FRNK contains several phosphorylation sites with unknown importance and function. Here I hypothesize that FRNK can inhibit FAK by binding directly to FAK within focal adhesions. Furthermore, I propose that serine phosphorylation at residue 217 of FRNK reduces its ability to bind to FAK, highlighting a potential regulatory mechanism for the newly described FAK-FRNK interaction. I found using co-immunoprecipitation and fluorescence resonance energy transfer that FRNK can bind directly to FAK. FRNK serine phosphorylation occurs in vitro and in vivo, and FRNK S217 is phosphorylated in an ERK-dependent fashion. Additionally, mutation of serine 217 on FRNK to alanine resulted in increased FAK binding. Cells overexpressing S217A FRNK exhibited increased rates of apoptosis as measured by flow cytometry. Taken together, I propose that FAK-FRNK complexes are an important mechanism of FRNK inhibition of FAK and that this mechanism is regulated by ERK phosphorylation of FRNK at serine 217. This information could be used to rationally develop treatments to treat diseases involving abnormal smooth muscle cell growth in response to injury, such as in-stent restenosis.

Creative Commons License

Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 License.

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