View Program - 63rd Annual Drosophila Research Conference

NUAK belongs to the AMP-activated protein kinase (AMPK) family, which is comprised of conserved serine/threonine protein kinases known to regulate cell polarity or cell motility by controlling the assembly and/or disassembly of cytoskeletal proteins. Previous results in our lab have demonstrated that a mutation in Drosophila NUAK results in the degeneration of larval body wall muscles. One prominent feature in these muscles is the abnormal accumulation of select proteins, which displaces other components of the contractile sarcomere apparatus. To better understand how kinase activity contributes to NUAK function, we mutated important residues in the conserved kinase domain using CRISPR/Cas9 and transgenic mutagenesis approaches. Indeed, mutation of a key catalytic residue within the kinase domain resulted in earlier lethality and thinner muscles. These results were confirmed by expressing a sallimus (Sls)-GFP fusion protein to visualize the dynamics of this process in vivo. Next we wanted to determine if we could separate the requirement for NUAK in embryonic muscle development from protein aggregation and muscle degeneration in larval contractile muscles. Compromising NUAK kinase activity in larval muscle using a post-embryonic driver still resulted in protein aggregation, thus suggesting that NUAK has independent functions in muscle development and muscle homeostasis. We have confirmed that a conserved threonine residue in the kinase domain of NUAK is essential to promote protein activity. To uncover proteins that may be substrates of NUAK kinase activity, we performed a yeast two-hybrid screen. l(2)elf, which encodes for CryAB, emerged as a top candidate since mutations in human CryAB/α-crystallin B cause a type of protein aggregate disease called Myofibrillar Myopathy. Our results thus far show that overexpression of NUAK increases CryAB phosphorylation and this post-translational modification can be reversed with phosphatase treatment. Taken together these data suggest that CryAB may be a target of NUAK phosphorylation in the prevention of protein aggregation.

CryAB is a target protein of NUAK kinase activity to prevent protein aggregation in muscle tissue