Suppression of scant identifies Endos as a substrate of greatwall kinase and a negative regulator of protein phosphatase 2A in mitosis.

Protein phosphatase 2A (PP2A) plays a major role in dephosphorylating the targets of the major mitotic kinase Cdk1 at mitotic exit, yet how it is regulated in mitotic progression is poorly understood. Here we show that mutations in either the catalytic or regulatory twins/B55 subunit of PP2A act as enhancers of gwl(Scant), a gain-of-function allele of the Greatwall kinase gene that leads to embryonic lethality in Drosophila when the maternal dosage of the mitotic kinase Polo is reduced. We also show that heterozygous mutant endos alleles suppress heterozygous gwl(Scant); many more embryos survive. Furthermore, heterozygous PP2A mutations make females heterozygous for the strong mutation polo(11) partially sterile, even in the absence of gwl(Scant). Heterozygosity for an endos mutation suppresses this PP2A/polo(11) sterility. Homozygous mutation or knockdown of endos leads to phenotypes suggestive of defects in maintaining the mitotic state. In accord with the genetic interactions shown by the gwl(Scant) dominant mutant, the mitotic defects of Endos knockdown in cultured cells can be suppressed by knockdown of either the catalytic or the Twins/B55 regulatory subunits of PP2A but not by the other three regulatory B subunits of Drosophila PP2A. Greatwall phosphorylates Endos at a single site, Ser68, and this is essential for Endos function. Together these interactions suggest that Greatwall and Endos act to promote the inactivation of PP2A-Twins/B55 in Drosophila. We discuss the involvement of Polo kinase in such a regulatory loop.

Inter-Relationships between Frailty, Sarcopenia, Undernutrition and Dysphagia in Older People Who Are Admitted to Acute Frailty and Medical Wards: Is There an Older Adult Quartet?

Introduction: With increasing age the prevalence of frailty, sarcopenia, undernutrition and dysphagia increases. These are all independent markers of outcome. This study explores the prevalence of these four and explores relationships between them. Methods: A convenience sample of 122 patients admitted to acute medical and frailty wards were recruited. Each was assessed using appropriate screening tools; Clinical Frailty Score (CFS) for frailty, SARC-F for sarcopenia, Nutritional Risk Tool (NRT) for nutritional status and 4QT for dysphagia. Results: The mean age of the participants was 80.53 years (65-99 years), and 50.37% (68) were female. Overall, 111 of the 122 (91.0%) reported the presence of at least one of the quartet. The median CFS was 5 (1-9), with 84 patients (68.9%) having a score of ≥5 (moderate or severely frail); The median SARC-F was 5 (0-10), with 64 patients (52.5%) having a score of ≥5; The median NRT was 0 (0-8) and 33 patients (27.0%) scored ≥ 1. A total of 77 patients (63.1%) reported no difficulty with swallowing/dysphagia (4QT ≥ 1) and 29 (23.7%) had only one factor. Sixteen patients (13.1%) had all four. There was a significant correlation between nutritional status and dysphagia, but not with frailty or sarcopenia. There were significant correlations between frailty and both sarcopenia and dysphagia. Conclusions: In our sample of acute medical and frailty ward patients, there was a much higher prevalence than expected (91%) of either: frailty, sarcopenia, undernutrition or dysphagia. The prevalence of all four was present in 13% of patients. We suggest that frailty, sarcopenia, nutritional risk and dysphagia comprise an "Older Adult Quartet". Further study is required to investigate the effect of the "Older Adult Quartet" on morbidity and mortality.