The human tumour suppressor LATS1 is activated by human MOB1 at the membrane Alexander Hergovich, Debora Schmitz, Brian A. Hemmings * Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66, CH-4058 Basel, Switzerland Received 29 March 2006 Available online 25 April 2006 Abstract Downregulation of the LATS1 tumour suppressor protein kinase contributes to tumour formation in mammals and flies. Strikingly, the tumour suppressor activity depends on the interaction with Dmob (Drosphila Mps1-One binder) in Drosophila melanogaster. Recent- ly, human LATS1 was reported to interact with human MOB1 (hMOB1), but the activation of LATS1 was not addressed. Here, we identified a highly conserved hMOB1-binding motif within LATS1’s primary structure. While co-expression of LATS1 with hMOB1 did not elevate LATS1 kinase activity in mammalian cells, membrane-targeting of hMOB1 resulted in a significant increase of LATS1 activity. This stimulation was dependent on intact activation segment and hydrophobic motif phosphorylation sites, and was further found to occur a few minutes after membrane association. Therefore, we suggest a potential in vivo mechanism of LATS1 activation through rapid recruitment to the plasma membrane by hMOB1 followed by multi-site phosphorylation, thereby providing insight into the molecular regulation of the LATS tumour suppressor. Ó 2006 Elsevier Inc. All rights reserved. Keywords: Signal transduction; LATS; Kinase; Tumour suppressor; MOB; Membrane; Activation mechanism The conserved NDR (nuclear Dbf2-related) family rep- resents a subclass of the AGC serine/threonine protein kinases and consists of mammalian NDR1, NDR2, LATS1 (large tumour suppressor 1) and LATS2, Drosophila mela- nogaster TRC and LATS, Caenorhabditis elegans SAX-1 and LATS, and a number of fungi and plant kinases [1]. Human, fly, and yeast NDR kinases have been reported to require phosphorylation on both the activation segment and the hydrophobic motif for activation [2–9]. All family members have also a conserved N-terminal regulatory (NTR) domain of different lengths, best characterized in mammalian NDR1/2 [8–12]. Human MOB1A (hMOB1A) binds to this domain, thereby probably releasing autoinhi- bition of activation segment autophosphorylation [10]. However, although this activation mechanism is readily recapitulated in vitro, co-expression of the various compo- nents in tissue culture cells proved inefficient to activate NDR1/2 kinases [10,11], but when NDR1/2 itself or its co-activator hMOB1A/B/2 (hMOBs) is targeted to the membrane, an increase in NDR1/2 kinase activity was readily achieved [11,13]. While the biological functions of mammalian NDR1/2 remain the subject of intense research, mammalian LATS kinases are implicated in regulating cell cycle progression and apoptosis [14–23]. Moreover, LATS1 deficient mice developed ovarian stromal cell tumours and soft tissue sar- comas [24]. Promoter inactivation and missense mutations affecting LATS1 have further been reported in human sar- comas, ovarian carcinomas, and breast cancer [25–27]. These data suggest that dysregulated LATS1 expression contributes to tumour formation in mammals. Strikingly, the warts/lats gene confers also tumour suppressor activity in invertebrates [28–30]. The signalling pathway involving Lats/Warts, Hippo, Salvador, and Yorkie proteins was previously shown to be essential for proliferation control in D. melanogaster 0006-291X/$ - see front matter Ó 2006 Elsevier Inc. All rights reserved. doi:10.1016/j.bbrc.2006.03.244 * Corresponding author. Fax: +41 61 697 3976. E-mail address: brian.hemmings@fmi.ch (B.A. Hemmings). www.elsevier.com/locate/ybbrc Biochemical and Biophysical Research Communications 345 (2006) 50–58 BBRC