Merlin, the protein product of the Neurofibromatosis type-2 gene, acts as a tumour suppressor in mice and humans. Merlin is an adaptor protein with a FERM domain and it is thought to transduce a growth-regulatory signal. However, the pathway through which Merlin acts as a tumour suppressor is poorly understood. Merlin, and its function as a negative regulator of growth, is conserved in Drosophila, where it functions with Expanded, a related FERM domain protein. Here, we show that Drosophila Merlin and Expanded are components of the Hippo signalling pathway, an emerging tumour-suppressor pathway. We find that Merlin and Expanded, similar to other components of the Hippo pathway, are required for proliferation arrest and apoptosis in developing imaginal discs. Our genetic and biochemical data place Merlin and Expanded upstream of Hippo and identify a pathway through which they act as tumour-suppressor genes.

Spinocerebellar ataxia type 1 (SCA1) is one of several neurodegenerative diseases caused by expansion of a polyglutamine tract in the disease protein, in this case, ATAXIN-1 (ATXN1). A key question in the field is whether neurotoxicity is mediated by aberrant, novel interactions with the expanded protein or whether its wild-type functions are augmented to a deleterious degree. We examined soluble protein complexes from mouse cerebellum and found that the majority of wild-type and expanded ATXN1 assembles into large stable complexes containing the transcriptional repressor Capicua. ATXN1 directly binds Capicua and modulates Capicua repressor activity in Drosophila and mammalian cells, and its loss decreases the steady-state level of Capicua. Interestingly, the S776A mutation, which abrogates the neurotoxicity of expanded ATXN1, substantially reduces the association of mutant ATXN1 with Capicua in vivo. These data provide insight into the function of ATXN1 and suggest that SCA1 neuropathology depends on native, not novel, protein interactions.

Transient Receptor Potential Melastatin-8 (TRPM8), a recently identified member of the transient receptor potential (TRP) family of ion channels, is activated by mild cooling and by chemical compounds such as the supercooling agent, icilin. Since cooling, possibly involving TRPM8 stimulation, diminishes injury-induced peripheral inflammation, we hypothesized that TRPM8 activation may also attenuate systemic inflammation. We thus studied the involvement of TRPM8 in regulating colonic inflammation using two mouse models of chemically induced colitis. TRPM8 expression, localized immunohistochemically in transgenic TRPM8 GFP mouse colon, was up-regulated in both human-and murine-inflamed colon samples, as measured by realtime PCR. Wild-type mice (but not TRPM8-nulls) treated systemically with the TRPM8 agonist, icilin showed an attenuation of chemically induced colitis, as reflected by a decrease in macroscopic and microscopic damage scores, bowel thickness, and myeloperoxidase activity compared with untreated animals. Furthermore, icilin treatment reduced the 2,4,6-trinitrobenzenesulfonic acid-induced increase in levels of inflammatory cytokines and chemokines in the colon. In comparison with wild-type mice, Dextran Sodium Sulfate (DSS)-treated TRPM8 knockout mice showed elevated colonic levels of the inflammatory neuropeptide calcitonin-gene-related peptide, although inflammatory indices were equivalent for both groups. Further, TRPM8 activation by icilin blocked capsaicin-triggered calcitonin-gene-related peptide release from colon tissue ex vivo and blocked capsaicin-triggered calcium signaling in Transient Receptor Potential Vaniloid-1 (TRPV1) and TRPM8 transfected HEK cells. Our data document an anti-inflammatory role for TRPM8 activation, in part due to an inhibiton of neuropeptide release, pointing to a novel therapeutic target for colitis and other inflammatory diseases.