Tiny Drosophila makes giant strides in cancer research

Cancer burden has been increasing worldwide, making cancer the second leading cause of death in the world. Over the past decades, various experimental models have provided important insights into the nature of cancer. Among them, the fruit fly Drosophila as a whole-animal toolkit has made a decisive contribution to our understanding of fundamental mechanisms of cancer development including loss of cell polarity. In recent years, scalable Drosophila platforms have proven useful also in developing anti-cancer regimens that are effective not only in mammalian models but also in patients. Here, we review studies using Drosophila as a tool to advance cancer study by complementing other traditional research systems.

AMPK regulates cell shape of cardiomyocytes by modulating turnover of microtubules through CLIP-170

AMP-activated protein kinase (AMPK) is a multifunctional kinase that regulates microtubule (MT) dynamic instability through CLIP-170 phosphorylation; however, its physiological relevance in vivo remains to be elucidated. In this study, we identified an active form of AMPK localized at the intercalated disks in the heart, a specific cell-cell junction present between cardiomyocytes. A contractile inhibitor, MYK-461, prevented the localization of AMPK at the intercalated disks, and the effect was reversed by the removal of MYK-461, suggesting that the localization of AMPK is regulated by mechanical stress. Time-lapse imaging analysis revealed that the inhibition of CLIP-170 Ser-311 phosphorylation by AMPK leads to the accumulation of MTs at the intercalated disks. Interestingly, MYK-461 increased the individual cell area of cardiomyocytes in CLIP-170 phosphorylation-dependent manner. Moreover, heart-specific CLIP-170 S311A transgenic mice demonstrated elongation of cardiomyocytes along with accumulated MTs, leading to progressive decline in cardiac contraction. In conclusion, these findings suggest that AMPK regulates the cell shape and aspect ratio of cardiomyocytes by modulating the turnover of MTs through homeostatic phosphorylation of CLIP-170 at the intercalated disks.

Shape of the glucose response curve during an oral glucose tolerance test is associated with insulin clearance and muscle insulin sensitivity in healthy non-obese men

Individuals with a monophasic glucose response curve (GRC) during a 75-g oral glucose tolerance test have a higher risk for type 2 diabetes than those with a biphasic GRC. However, no studies have addressed the association between GRC type and insulin clearance. Thus, we studied 49 healthy non-obese Japanese men. We divided study participants into the monophasic or biphasic group based on the shape of their GRC. We evaluated tissue-specific insulin sensitivity and insulin clearance using a two-step hyperinsulinemic-euglycemic clamp. The monophasic group had more visceral fat, lower insulin clearance and lower muscle insulin sensitivity than the biphasic group, whereas liver and adipose tissue insulin sensitivity, and insulin secretion were comparable. In conclusion, healthy non-obese men with a monophasic GRC have lower insulin clearance and muscle insulin sensitivity.