High impact information on mbt

• The Drosophila Ste20 family kinase dMST functions as a tumor suppressor by restricting cell proliferation and promoting apoptosis [1].
• The data presented here genetically link msn to two distinct biological events, dorsal closure and photoreceptor axon pathfinding, and thus provide the first evidence that Ste20 kinases of the germinal center kinase family play a role in axonal pathfinding [2].
• The Ste20 kinase misshapen regulates both photoreceptor axon targeting and dorsal closure, acting downstream of distinct signals [2].
• Besides regulation of kinase activity, another important function of Cdc42 is to recruit Mbt to adherens junctions [3].
• The Drosophila gene mushroom bodies tiny (mbt) encodes a putative p21-activated kinase (PAK), a family of proteins that has been implicated in a multitude of cellular processes including regulation of the cytoskeleton, cell polarisation, control of MAPK signalling cascades and apoptosis [3].

Biological context of mbt

• In this study we undertook a genetic approach to identify proteins acting in the Mbt signalling pathway during photoreceptor cell morphogenesis [4].
• Constitutive activation of Mbt not only disturbs the actin cytoskeleton but also affects adherens junction organisation indicating a requirement of the protein in cell adhesion dependent processes during photoreceptor cell differentiation [4].
• The mutant phenotype of mbt is characterised by fewer neurones in the brain and the eye, indicating a role of the protein in cell proliferation, differentiation or survival [3].
• We show that mbt repeat alleles produce stable SCM proteins that associate with normal sites in polytene chromosomes [5].
• The coding protein contained the SPM domain and mbt repeats, both of which are characteristic of the PcG proteins, and showed significant similarity in amino acid sequence to the Drosophila Sex comb on midleg (Scm) protein [6].

Anatomical context of mbt

• We show that mutations in mbt primarily interfere with the generation or survival of the intrinsic cells (Kenyon cells) of the mushroom body, a paired neuropil structure in the adult brain involved in learning and memory [7].

Associations of mbt with chemical compounds

• The recovered cDNA encodes two mbt repeats and the SPM domain that characterize Scm, but lacks the cysteine clusters and the serine/threonine-rich region found at the amino terminus of Scm [8].
• Four recent papers describe the characterization in Drosophila of Hippo, a serine/threonine kinase of the Sterile 20 (STE20) group, resembling Mst1 and Mst2 [9].
• Based on the alignment of 12 sequences of protein motifs that interact with the kinases SPAK (Ste20-related proline alanine-rich kinase) and OSR1 (oxidative stress response 1), we performed genome-wide searches of the sequence [S/G/V]RFx[V/I]xx[V/I/T/S]xx, where x represents any amino acid [10].

Regulatory relationships of mbt

• The Drosophila p21 activated kinase Mbt regulates the actin cytoskeleton and adherens junctions to control photoreceptor cell morphogenesis [4].

Other interactions of mbt

• For two of the three known Pak proteins in Drosophila melanogaster, D-Pak and Mbt, distinct functions during eye development have been established [4].

Analytical, diagnostic and therapeutic context of mbt

• In a genetic screen for mutations that restrict cell growth and organ size, we identified a new tumor suppressor gene, dMST, which encodes the Drosophila homolog of the mammalian Ste20 kinase family members MST1 and MST2 [1].

References