Investigating the function of the non-receptor tyrosine kinase, SRMS

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Tyrosine kinases are enzymes that control various biological processes that underlie overall cell and organismal growth. Cell growth, division, motility, and differentiation are key examples of such processes regulated by tyrosine kinases. Src-related kinase lacking C-terminal regulatory tyrosine and N-terminal myristoylation sites (SRMS) is a tyrosine kinase that is conserved across many species, including humans, mice, and zebra fish. It is also the least studied and understood of the 90 known tyrosine kinases expressed in vertebrate species. SRMS is a member a non-receptor type tyrosine kinase family known as the BRK family kinases (BFKs). BRK (Breast tumor kinase, gene name PTK6) and FRK (Fyn-related kinase) are the other two proteins that belong to this family. Both PTK6 and FRK have been extensively characterized and shown to play key cellular roles in the context of cell growth and motility. The cellular and physiological roles of SRMS, on the other hand, remain largely unknown. In 2013, our group published the first biochemical study and revealed that (a) the 50 amino-acid long N-terminal region of the SRMS protein regulates its enzymatic activity and (b) Dok1 is the first bona fide cellular substrate of SRMS. Here, I propose a new program that seeks to decipher the cellular and biochemical role of SRMS by identifying the SRMS substrates/regulated proteins (phosphoproteomics) via quantitative mass spectrometry analyses. We also aim to characterize PTK6 as a SRMS. The validation and characterization of the hits is the major part of the short-term goals of the program, which will involve current and future trainees and will all be conducted in my laboratory. We will validate and characterize the SRMS targets using a myriad of molecular techniques employed in my laboratory, such as reciprocal immunoprecipitation, GST-pulldown assays, site-directed mutagenesis, in vitro kinase assays, and confocal immunofluorescence microscopy, to name a few. Therefore, here I propose to accelerate my existing research program on SRMS and thus meaningfully contribute to a career-long goal of understanding the cellular and physiological role of SRMS and how the function of SRMS differs from PTK6, FRK, and other tyrosine kinases. Our long-term goals specific to SRMS involve developing and adapting applied proteomics knowledge using high-throughput peptide-microarrays towards understanding SRMS-regulated signalosomes. We further propose to cumulatively employ these proteomics strategies towards understanding the cellular kinetics, associated signaling pathways, and mechanism of function, all in the context of investigating the cellular and physiological roles of the BFKs. Overall, these studies can be further adapted to understand how the role of SRMS impacts vertebrate biology at large.