Control of mitotic events by the Cdc42 GTPase, the Clb2 cyclin and a member of the PAK kinase family.

BACKGROUND: Cyclins and cyclin-dependent kinases induce and coordinate the events of the cell cycle, although the mechanisms by which they do so remain largely unknown. In budding yeast, a pathway used by the Clb2 cyclin to control bud growth during mitosis provides a good model system in which to understand how cyclin-dependent kinases control cell-cycle events. In this pathway, Clb2 initiates a series of events that lead to the mitosis-specific activation of the Gin4 protein kinase. A protein called Nap1 is required in vivo for the activation of Gin4, and is able to bind to both Gin4 and Clb2. We have used a simple genetic screen to identify additional proteins that function in this pathway. RESULTS: We have found that the Cdc42 GTPase and a member of the PAK kinase family called Cla4 both function in the pathway used by Clb2 to control bud growth during mitosis. Cdc42 and Cla4 interact genetically with Gin4 and Nap1, and both are required in vivo for the mitosis-specific activation of the Gin4 kinase. Furthermore, Cla4 undergoes a dramatic hyperphosphorylation in response to the combined activity of Nap1, the Clb2-Cdc28 kinase complex, and the GTP-bound form of Cdc42. Evidence is presented which suggests that the hyperphosphorylated form of Cla4 is responsible for relaying the signal to activate Gin4. CONCLUSIONS: Previous studies have suggested that cyclin-dependent kinases control the cell cycle by directly phosphorylating proteins involved in specific events, such as nuclear lamins, microtubule-associated proteins and histones. In contrast, our results demonstrate that the Clb2-Cdc28 cyclin-dependent kinase complex controls specific cell-cycle events through a pathway that involves a GTPase and at least two different kinases. This suggests that cyclin-dependent kinases may control many cell-cycle events through GTPase-linked signaling pathways that resemble the intricate signaling pathways known to control many other cellular events.

The dynein genes of Paramecium tetraurelia. Sequences adjacent to the catalytic P-loop identify cytoplasmic and axonemal heavy chain isoforms.

Paramecium tetraurelia is a unicellular organism that utilizes both axonemal and cytoplasmic dyneins. The highly conserved region containing the catalytic P-loop of the dynein heavy chain was amplified by RNA-directed polymerase chain reaction. Eight different P-loop-containing cDNA fragments were cloned. Southern hybridization analysis indicated that each fragment corresponds to a separate dynein gene and that there are at least 12 dynein heavy chain genes expressed in Paramecium. Seven of the eight cloned contain sequence motif A, which is found in axonemal dyneins, and one contains sequence motif B, which is found in the dyneins from cell types that do not have cilia or flagella. Two of the Paramecium dynein genes were further investigated: DHC-6 which contains motif A, and DHC-8 which contains motif B. Additional sequencing of the central portions of these genes showed that DHC-6 most closely matches sea urchin ciliary beta heavy chain and DHC-8 is similar to the cytoplasmic dynein from Dictyostelium. Deciliation of the cells resulted in a substantial increase in the steady state concentration of DHC-6 mRNA but only a small change in DHC-8 mRNA. Antisera were produced against synthetic peptides derived from sequence motifs A and B. Competitive solid-phase binding assays demonstrated that each antiserum was peptide-specific. In western blots, the antiserum to motif A reacted with both ciliary and cytoplasmic dyneins. In contrast, the antiserum to motif B reacted with the cytoplasmic dyneins of Paramecium and bovine brain but did not react with ciliary dynein.(ABSTRACT TRUNCATED AT 250 WORDS)

Management of dengue shock syndrome. A prospective study.

Since dengue hemorrhagic fever (DHF) was first reported 20 years ago, the only serious variant of the disease, dengue shock syndrome (DSS), still continues to cause a relatively high mortality. An effective yet simple management of DSS which can be carried out in every hospital is certainly necessary if the dead toll is to be reduced. Prospective study of a simple procedure in managing DSS patients in Bhayangkara Police Hospital Kediri is reported. Depends on the severity of the disease, for DHF grade III: 30 ml/kg bw Lactated-Ringer solution was given at free rate. This is followed by 20 ml/kg bw of synthetic plasma expander (Expafusin) in a rate of thrice the body weight and continued with lactated-ringer and 5% dextrose in 1/2 Saline alternately with a rate of twice the body weight per minute for the remaining first 24 hours. For DHF grade IV, the same fluids were given, except for the amount and the infusion rate. Drugs administered and medical care were all the same for both groups. A close observation, a critical assessment, and an accurate as well as a rapid action are very important factors. Totally there were 115 patients of which 8 died. The mortality rate was 7%. A better management and/or treatment has to be developed to further reduce the mortality.