We have identified the human homologue of a regulatory cofactor of Na -H؉ exchanger NHE3 to which it is thought to bind via one of its two PDZ domains. The carboxyl-terminal region of NHE-RF, downstream of the PDZ domains, interacts with the amino-terminal protein 4.1 domain-containing segment of merlin in yeast twohybrid assays. This interaction also occurs in affinity binding assays with full-length NHE-RF expressed in COS-7 cells. NHE-RF binds to the related ERM proteins, moesin and radixin. We have localized human NHE-RF to actin-rich structures such as membrane ruffles, microvilli, and filopodia in HeLa and COS-7 cells, where it co-localizes with merlin and moesin. These findings suggest that hNHE-RF and its binding partners may participate in a larger complex (one component of which might be a Na ؉ -H ؉ exchanger) that could be crucial for the actin filament assembly activated by the ERM proteins and for the tumor suppressor function of merlin.Neurofibromatosis 2 (NF2), 1 is a dominantly inherited disorder characterized by bilateral occurrence of vestibular schwannomas and other brain tumors, especially meningiomas, and schwannomas of other cranial nerves and spinal nerve roots (1). The NF2 gene isolated by positional cloning encodes merlin, named for its striking similarity with moesin, ezrin, and radixin, three closely related proteins commonly referred to as the ERM family, a subclass of the protein 4.1 superfamily thought to link cytoskeletal components with proteins in the cell membrane (2, 3). The ERM proteins share ϳ78% amino acid identity with each other, and all three are 45-47% identical to merlin (4).In cultured cells, ERM proteins are highly concentrated in regions of contact between actin filaments and the plasma membrane, acting as possible linkers between integral membrane and cytoskeletal proteins (5-9). The carboxyl termini of both ezrin and moesin bind directly to actin in vitro (10, 11) via a conserved actin binding site present in ezrin, moesin, and radixin but not in merlin. These findings suggest that the carboxyl terminus of the ERM proteins is responsible for their association with the actin-based cytoskeleton. Recently, however, another actin binding site in the amino-terminal domain of ezrin has been characterized in vitro and shown to be conserved in moesin, radixin, and merlin (12). The highly conserved amino-terminal half of the ERM proteins also contains the domain responsible for interaction with membrane proteins, particularly the glycoprotein CD44 (13). ERM-CD44 complexes are also associated with RhoGDI (RhoGDP dissociation inhibitor) (14), and the ERM proteins have been directly implicated in Rho-and Rac-dependent cytoskeletal reorganization in permeabilized cells (15).We have reported that endogenous merlin localizes to the actin-rich motile regions (i.e. leading and ruffling edges) in human fibroblast and meningioma cells where it co-localizes with actin but is not associated with stress fibers (16). Merlin when overexpressed in cells, however, localizes to membrane ruf...

We describe a method to decipher the complex inter-relationships between metabolite production trends and gene expression events, and show how information gleaned from such studies can be applied to yield improved production strains. Genomic fragment microarrays were constructed for the Aspergillus terreus genome, and transcriptional profiles were generated from strains engineered to produce varying amounts of the medically significant natural product lovastatin. Metabolite detection methods were employed to quantify the polyketide-derived secondary metabolites lovastatin and (+)-geodin in broths from fermentations of the same strains. Association analysis of the resulting transcriptional and metabolic data sets provides mechanistic insight into the genetic and physiological control of lovastatin and (+)-geodin biosynthesis, and identifies novel components involved in the production of (+)-geodin, as well as other secondary metabolites. Furthermore, this analysis identifies specific tools, including promoters for reporter-based selection systems, that we employed to improve lovastatin production by A. terreus.

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