Plant aquaporins form a large protein family including plasma membrane-type (PIPs) and tonoplast-type aquaporins (TIPs), and facilitate osmotic water transport across membranes as a key physiological function. We identified 33 genes for aquaporins in the genome sequence of rice (Oryza sativa L. cv. Nipponbare). We investigated their expression levels in leaf blades, roots and anthers of rice (cv. Akitakomachi) using semi-quantitative reverse transcription-PCR (RT-PCR). At both early tillering (21 d after germination) and panicle formation (56 d) stages, six genes, including OsPIP2;4 and OsPIP2;5, were expressed predominantly in roots, while 14 genes, including OsPIP2;7 and OsTIP1;2, were found in leaf blades. Eight genes, such as OsPIP1;1 and OsTIP4;1, were evenly expressed in leaf blades, roots and anthers. Analysis by stopped-flow spectrophotometry revealed high water channel activity when OsPIP2;4 or OsPIP2;5 were expressed in yeast but not when OsPIP1;1 or OsPIP1;2 were expressed. Furthermore, the mRNA levels of OsPIP2;4 and OsPIP2;5 showed a clear diurnal fluctuation in roots; they showed a peak 3 h after the onset of light and dropped to a minimum 3 h after the onset of darkness. The mRNA levels of 10 genes including OsPIP2;4 and OsPIP2;5 markedly decreased in roots during chilling treatment and recovered after warming. The changes in mRNA levels during and after the chilling treatment were comparable with that of the bleeding sap volume. These results suggested the relationship between the root water uptake and mRNA levels of several aquaporins with high water channel activity, such as OsPIP2;4 and OsPIP2;5.

A polarity complex of PAR-3, PAR-6 and atypical protein kinase C (aPKC) functions in various cell-polarization events, including neuron specification. The small GTPase Cdc42 binds to PAR-6 and regulates cell polarity. However, little is known about the downstream signals of the Cdc42-PAR protein complex. Here, we found that PAR-3 directly interacted with STEF/Tiam1, which are Rac-specific guanine nucleotide-exchange factors, and that STEF formed a complex with PAR-3-aPKC-PAR-6-Cdc42-GTP. Cdc42 induces lamellipodia in a Rac-dependent manner in N1E-115 neuroblastoma cells. Disruption of Cdc42-PAR-6 or PAR-3-STEF binding inhibited Cdc42-induced lamellipodia but not filopodia. The isolated STEF-binding PAR-3 fragment was sufficient to induce lamellipodia independently of Cdc42 and PAR-6. PAR-3 is required for Cdc42-induced Rac activation, but is not essential for lamellipodia formation itself. In cultured hippocampal neurons, STEF accumulated at the tip of the growing axon and colocalized with PAR-3. The spatio-temporal activation and signalling of Cdc42-PAR-6-PAR-3-STEF/Tiam1-Rac seem to be involved in neurite growth and axon specification. We propose that the PAR-6-PAR-3 complex mediates Cdc42-induced Rac activation by means of STEF/Tiam1, and that this process seems to be required for the establishment of neuronal polarity.

We and others previously identified NKX2-1, also known as TITF1 and TTF-1, as a lineage-survival oncogene in lung adenocarcinomas. Here we show that NKX2-1 induces the expression of the receptor tyrosine kinase-like orphan receptor 1 (ROR1), which in turn sustains a favorable balance between prosurvival PI3K-AKT and pro-apoptotic p38 signaling, in part through ROR1 kinase-dependent c-Src activation, as well as kinase activity-independent sustainment of the EGFR-ERBB3 association, ERBB3 phosphorylation, and consequential PI3K activation. Notably, ROR1 knockdown effectively inhibited lung adenocarcinoma cell lines, irrespective of their EGFR status, including those with resistance to the EGFR tyrosine kinase inhibitor gefitinib. Our findings thus identify ROR1 as an "Achilles' heel" in lung adenocarcinoma, warranting future development of therapeutic strategies for this devastating cancer.

Neurons polarize to form elaborate multiple dendrites and one long axon. The establishment and maintenance of axon/dendrite polarity are fundamentally important for neurons. Recent studies have demonstrated that the polarity complex PAR-3-PAR-6-atypical protein kinase C (aPKC) is involved in polarity determination in many tissues and cells. The function of the PAR-3-PAR-6-aPKC protein complex depends on its subcellular localization in polarized cells. PAR-3 accumulates at the tip of growing axons in cultured rat hippocampal neurons, but the molecular mechanism of this localization remains unknown. Here we identify a direct interaction between PAR-3 and KIF3A, a plus-end-directed microtubule motor protein, and show that aPKC can associate with KIF3A through its interaction with PAR-3. The expression of dominant-negative PAR-3 and KIF3A fragments that disrupt PAR-3-KIF3A binding inhibited the accumulation of PAR-3 and aPKC at the tip of the neurites and abolished neuronal polarity. These results suggest that PAR-3 is transported to the distal tip of the axon by KIF3A and that the proper localization of PAR-3 is required to establish neuronal polarity.

Axon growth during neural development is highly dependent on both cytoskeletal re-organization and polarized membrane trafficking. Previously, we demonstrated that collapsin response mediator protein-2 (CRMP-2) is critical for specifying axon/dendrite fate and axon growth in cultured hippocampal neurons, possibly by interacting with tubulin heterodimers and promoting microtubule assembly. Here, we identify Numb as a CRMP-2-interacting protein. Numb has been shown to interact with alpha-adaptin and to be involved in endocytosis. We found that Numb was associated with L1, a neuronal cell adhesion molecule that is endocytosed and recycled at the growth cone, where CRMP-2 and Numb were colocalized. Furthermore, expression of dominant-negative CRMP-2 mutants or knockdown of CRMP-2 message with small-interfering (si) RNA inhibited endocytosis of L1 at axonal growth cones and suppressed axon growth. These results suggest that in addition to regulating microtubule assembly, CRMP-2 is involved in polarized Numb-mediated endocytosis of proteins such as L1.