Menopause is associated with bone loss and enhanced visceral adiposity. We have shown previously that a polyclonal antibody (Ab) to the β-subunit of the pituitary hormone Fsh increases bone mass in mice. Here, we report that this Ab sharply reduces adipose tissue in wild type mice, phenocopying genetic Fshr haploinsufficiency. The Ab also causes profound beiging, increases cellular mitochondrial density, activates brown adipose tissue, and enhances thermogenesis. These actions result from the specific binding of Ab to Fshβ to block its action. Our studies uncover novel opportunities for co-treating obesity and osteoporosis.

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Highlights d SMAPs bind at an intersubunit pocket defined by all three PP2A subunits d DT-061 (SMAP) binding results in selective stabilization of PP2A-B56a heterotrimers d Stabilization of B56a heterotrimers biases PP2A toward substrates such as c-Myc d Accumulation of methylated, B56a heterotrimers, is a potential clinical biomarker

Kinase inhibitor resistance constitutes a major unresolved clinical challenge in cancer. Furthermore, the role of serine/threonine phosphatase deregulation as a potential cause for resistance to kinase inhibitors has not been thoroughly addressed. We characterize protein phosphatase 2A (PP2A) activity as a global determinant of KRAS-mutant lung cancer cell resistance across a library of >200 kinase inhibitors. The results show that PP2A activity modulation alters cancer cell sensitivities to a large number of kinase inhibitors. Specifically, PP2A inhibition ablated mitogen-activated protein kinase kinase (MEK) inhibitor response through the collateral activation of AKT/mammalian target of rapamycin (mTOR) signaling. Combination of mTOR and MEK inhibitors induced cytotoxicity in PP2A-inhibited cells, but even this drug combination could not abrogate MYC up-regulation in PP2A-inhibited cells. Treatment with an orally bioavailable small-molecule activator of PP2A DT-061, in combination with the MEK inhibitor AZD6244, resulted in suppression of both p-AKT and MYC, as well as tumor regression in two KRAS-driven lung cancer mouse models. DT-061 therapy also abrogated MYC-driven tumorigenesis. These data demonstrate that PP2A deregulation drives MEK inhibitor resistance in KRAS-mutant cells. These results emphasize the need for better understanding of phosphatases as key modulators of cancer therapy responses.

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