蓝藻运动及其调控机制概述

蓝藻运动是蓝藻积极适应外部环境的体现。根据蓝藻种类及运动方式不同可将蓝藻运动概括为三类: 即蓝藻泳动、蓝藻蹭动、蓝藻滑动。文章综述了蓝藻运动的相关研究进展, 对蓝藻不同运动方式进行描述, 并对蓝藻各种运动方式可能产生机制进行了总结, 列举了未来研究蓝藻运动需要解答的问题。     

Pseudomonas aeruginosa exhibits sliding motility in the absence of type IV pili and flagella

Pseudomonas aeruginosa exhibits swarming motility on 0.5 to 1% agar plates in the presence of specific carbon and nitrogen sources. We have found that PAO1 double mutants expressing neither flagella nor type IV pili (fliC pilA) display sliding motility under the same conditions. Sliding motility was inhibited when type IV pilus expression was restored; like swarming motility, it also decreased in the absence of rhamnolipid surfactant production. Transposon insertions in gacA and gacS increased sliding motility and restored tendril formation to spreading colonies, while transposon insertions in retS abolished motility. These changes in motility were not accompanied by detectable changes in rhamnolipid surfactant production or by the appearance of bacterial surface structures that might power sliding motility. We propose that P. aeruginosa requires flagella during swarming to overcome adhesive interactions mediated by type IV pili. The apparent dependence of sliding motility on environmental cues and regulatory pathways that also affect swarming motility suggests that both forms of motility are influenced by similar cohesive factors that restrict translocation, as well as by dispersive factors that facilitate spreading. Studies of sliding motility may be particularly well-suited for identifying factors other than pili and flagella that affect community behaviors of P. aeruginosa.     

Bacterial motility complexes require the actin‐like protein,MreB and the Ras homologue,MglA

Gliding motility in the bacterium Myxococcus xanthus uses two motility engines: S‐motility powered by type‐IV pili and A‐motility powered by uncharacterized motor proteins and focal adhesion complexes. In this paper, we identified MreB, an actin‐like protein, and MglA, a small GTPase of the Ras superfamily, as essential for both motility systems. A22, an inhibitor of MreB cytoskeleton assembly, reversibly inhibited S‐ and A‐motility, causing rapid dispersal of S‐ and A‐motility protein clusters, FrzS and AglZ. This suggests that the MreB cytoskeleton is involved in directing the positioning of these proteins. We also found that a ΔmglA motility mutant showed defective localization of AglZ and FrzS clusters. Interestingly, MglA–YFP localization mimicked both FrzS and AglZ patterns and was perturbed by A22 treatment, consistent with results indicating that both MglA and MreB bind to motility complexes. We propose that MglA and the MreB cytoskeleton act together in a pathway to localize motility proteins such as AglZ and FrzS to assemble the A‐motility machineries. Interestingly, M. xanthus motility systems, like eukaryotic systems, use an actin‐like protein and a small GTPase spatial regulator.     

The effects of carnitine,glycerylphosphorylcholine, caffeine,and egg yolk on the motility of rat epididymal spermatozoa

Experiments were performed to further the understanding of epididymal processes involved in the acquisition of sperm motility. Samples of luminal contents were collected by micropuncture from four regions of the rat epididymis. These samples were incubated in various diluents to observe the effects of the diluents on sperm motility. Consonant with previous reports, 40 mM glycerylphosphorylcholine (GPC) and 60 mM DL-carnitine reduced overall motility scores of cauda epididymidal spermatozoa but did not prevent normal initiation of motility. Additionally, control sperm cells and cells treated with carnitine could reinitiate full motility after becoming immotile. Spermatozoa treated with GPC could not reinitiate motility. The sperm cells in our system thus react to GPC and carnitine in fundamentally different ways, the exact nature of which remains to be determined. Spermatozoa from the distal caput epididymidis evidenced high motility scores when diluted in a 5% egg yolk + 10 mM caffeine diluent. It was demonstrated, however, that the subjective appearance of full motility in these immature cells was not supported by actual progressive motility as measured in an assay of linear distance traveled. It was concluded that neither 10 mM caffeine, 5% egg yolk, nor their combination was sufficient to induce progressive motility in immature rat spermatozoa.     

Two egg-derived molecules in sperm motility initiation and fertilization in the Pacific herring (Clupea pallasi)

Sperm of the Pacific herring are immotile at spawning. Two egg-derived molecules are capable of initiating sperm motility. One is herring sperm activating protein(s) (HSAPs) and the other is sperm motility initiation factor (SMIF). These two motility initiators differ in their location and association with the chorion, and in thier isoelectric points and molecular weights. In this study we have investigated the roles of these two inducers with respect to motility and fertilization. Using computer analysis of sperm motility, we found that HSAPs, as well as the C-terminal HSAPs peptide, elicit a linear motility pattern, while SMIF induced a highly circular and asymmetric pattern. HSAPs induced a two-fold increase in intracellular calcium, whereas SMIF induced a four-fold increase of motility initiation. SMIF-exposed sperm, preloaded with BAPTA-AM, showed a more linear motility and this motility trajectory decreased with their fertilizing capability. The difference in intracellular calcium levels between HSAPs and SMIF is consistent with the observed linear and circular motility. In the absence of SMIF, HSAPs do not support fertilization. Fertilization is rescued in these experiments if SMIF is reintroduced. We propose that diffusible HSAPs are not essential for fertilization, but enhance sperm-egg collisions via linear motility. SMIF, which is bound to the micropylar region of the chorion, is required for fertilization and induces circular motility that is a prerequisite for sperm to enter the micropylar canal and fertilize the egg.     

C-FLIP promotes the motility of cancer cells by activating FAK and ERK, and increasing MMP-9 expression

We examined the role of c-FLIP in the motility of HeLa cells. A small interfering RNA (siRNA) directed against c-FLIP inhibited the adhesion and motility of the cells without affecting their growth rate. The long form of c-FLIP (c-FLIPL), but not the short form (c-FLIPS), enhanced adhesion and motility. Downregulation of c-FLIPL with siRNA decreased phosphorylation of FAK and ERK, while overexpression of c-FLIPL increased their phosphorylation. Overexpression of FAK activated ERK, and enhanced the motility of HeLa cells. FRNK, an inhibitory fragment of FAK, inhibited ERK and decreased motility. Inhibition of ERK also significantly suppressed c-FLIPL-promoted motility. Inhibition of ROCK by Y27632 suppressed the c-FLIPL-promoted motility by reducing phosphorylation of FAK and ERK. Overexpression of c-FLIPL increased the expression and secretion of MMP-9, and inhibition of MMP-9 by Ilomastat reduced c-FLIPL- promoted cell motility. A caspase-like domain (amino acids 222-376) was found to be necessary for the c-FLIPL-promoted cell motility. We conclude that c-FLIPL promotes the motility of HeLa cells by activating FAK and ERK, and increasing MMP-9 expression.     

Activation of sperm motility in striped bass via a cAMP-independent pathway

The objective of the present study was to identify the effect of osmolality, ions (K+, H+, Ca2+, Mg2+) and cAMP on the initiation of sperm motility in striped bass (Morone saxatilis). Striped bass spermatozoa remained motile in solutions isotonic to seminal plasma (350 mOsm/kg) until osmolality reached 600 mOsm/kg. K+ (0-100 mM) had no effect ( p>0.05 ) on sperm motility, and sperm displayed a high percentage of motility over a wide range of pH (6.0-8.5). Sperm motility could be initiated in Ca2+-free solutions. In contrast, sperm motility was inhibited (P<0.01) by solutions containing > or =10 mM Ca2+, and sperm could not be reactivated by a Ca2+-free solution. This Ca2+ inhibition was not affected by verapamil, a Ca2+ channel blocker. However, if sperm motility was first initiated in a Ca2+-free solution, the addition of Ca2+ solutions, up to 80 mM, failed to inhibit sperm motility, suggesting that Ca2+ inhibited the initiation of motility, but had no control of motile spermatozoa. Mg2+ solutions had similar inhibitory effects on sperm motility as Ca2+ solutions. Therefore, initiation of motility in striped bass sperm may be related to voltage-gated channels across the cell's plasma membrane. Membrane permeable cAMP did not initiate motility of quiescent, intact striped bass spermatozoa, and motility of demembranated sperm could be activated in the absence of cAMP.     

Effects of oleic acid and bile salts on canine villous motility

The effects on canine villous motility of mucosal Tyrodes solution containing oleic acid (10 mM) and/or either taurocholic or cholic acid (15 mM) in the presence or absence of IV atropine (1 mg/kg) was used to assess the neural mediation of the effects of luminal nutrients. Villous motility was measured over 12 min periods by in vivo videomicroscopy of segments of jejunum. Neither bile salt had effects alone but villous motility increased after oleic acid was added to taurocholate and decreased after oleic acid was added to cholate. Villous motility increased when taurocholate and oleic acid were present initially and returned to control levels when removed. Villous motility was not affected by cholate and oleic acid but villous motility decreased when they were removed from the Tyrodes solution. Atropine blocked the increase in villous motility caused by taurocholate and oleic acid. Bile salts can modify the effect of oleic acid on villous motility and a cholinergic step is involved in the stimulation of motility.     

The beta1 integrin activates JNK independent of CagA, and JNK activation is required for Helicobacter pylori CagA+-induced motility of gastric cancer cells

The Helicobacter pylori CagA protein is translocated into gastric epithelial cells through a type IV secretion system (TFSS), and published studies suggest CagA is critical for H. pylori-associated carcinogenesis. CagA is thought to be necessary and sufficient to induce the motogenic response observed in response to CagA+ strains, as CagA interacts with proteins involved in adhesion and motility. We report that H. pylori strain 60190 stimulated AGS cell motility through a CagA- and TFSS-dependent mechanism, because strains 60190DeltacagA or 60190DeltacagE (TFSS-defective) did not increase motility. The JNK pathway is critical for H. pylori-dependent cell motility, as inhibition using SP600125 (JNK1/2/3 inhibitor) or a JNK2/3-specific inhibitor blocked motility. JNK mediates H. pylori-induced cell motility by activating paxillin, because JNK inhibition blocked paxillinTyr-118 phosphorylation, and paxillin expression knockdown completely abrogated bacteria-induced motility. Furthermore, JNK and paxillinTyr-118 were activated by 60190DeltacagA but not 60190DeltacagE, demonstrating CagA-independent signaling critical for cell motility. A beta1 integrin-blocking antibody significantly inhibited JNK and paxillinTyr-118 phosphorylation and cell scattering, demonstrating that CagA-independent signaling required for cell motility occurs through beta1. The requirement of both Src and focal adhesion kinase for signaling and motility further suggests the importance of integrin signaling in H. pylori-induced cell motility. Finally, we show that JNK activation occurs independent of known upstream kinases and signaling molecules, including Nod1, Cdc42, Rac1, MKK4, and MKK7, which demonstrates novel signaling leading to JNK activation. We report for the first time that H. pylori mediates CagA-independent signaling that promotes cell motility through the beta1 integrin pathway.     

Concerted action between Ca2+ and hyperosmolality initiates sperm motility in amphioxus Branchiostoma belcheri tsingtauense

This study investigated the effects of different environmental conditions on the initiation and maintenance of sperm motility in amphioxus Branchiostoma belcheri tsingtauense. The findings were that: (1) hyperosmolality in the absence of Ca(2+) ions did not initiate amphioxus sperm motility; (2) addition of Ca(2+) into EGTA-containing Ca(2+)-free artificial sea water (ASW), in which no sperm were motile, restored sperm motility; (3) Ca(2+) failed to induce sperm motility under conditions of hypoosmolality; (4) K(+) channel blockers quinine and 4-aminopiridine did not suppress the initiation of sperm motility; and (5) changes in pH did not cause sperm motility in a solution isotonic to seawater without Ca(2+). In conclusion, we inferred that a concerted action between Ca(2+) and hyperosmolality was essential to initiate motility of amphioxus sperm, whereas K(+) and pH were indispensable to maintain motility.     

complex interplay between type 1 fimbrial expression and flagellum-mediated motility of uropathogenic Escherichia coli

Type 1 fimbriae and flagella have been previously shown to contribute to the virulence of uropathogenic Escherichia coli (UPEC) within the urinary tract. In this study, the relationship between motility and type 1 fimbrial expression was tested for UPEC strain CFT073 by examining the phenotypic effect of fimbrial expression on motility and the effect that induction of motility has on type 1 fimbrial expression. While constitutive expression of type 1 fimbriae resulted in a significant decrease in motility and flagellin expression (P < 0.0001), a loss of type 1 fimbrial expression did not result in increased motility. Additionally, hypermotility and flagellar gene over- and underexpression were not observed to affect the expression of type 1 fimbriae. Hence, it appeared that the relationship between type 1 fimbrial expression and motility is unidirectional, where the overexpression of type 1 fimbriae dramatically affects motility and flagellum expression but not vice versa. Moreover, the constitutive expression of type 1 fimbriae in UPEC cystitis isolate F11 and the laboratory strain E. coli K-12 MG1655 also resulted in decreased motility, suggesting that this phenomenon is not specific to CFT073 or UPEC in general. Lastly, by analyzing the repression of motility caused by constitutive type 1 fimbrial expression, it was concluded that the synthesis and presence of type 1 fimbriae at the bacterial surface is only partially responsible for the repression of motility, as evidenced by the partial restoration of motility in the CFT073 fim L-ON DeltafimAICDFGH mutant. Altogether, these data provide further insight into the complex interplay between type 1 fimbrial expression and flagellum-mediated motility.     

Bidirectional regulation of hippocampal mossy fiber filopodial motility by kainate receptors: a two-step model of synaptogenesis

The rapid motility of axonal filopodia and dendritic spines is prevalent throughout the developing CNS, although the function of this motility remains controversial. Using two-photon microscopy, we imaged hippocampal mossy fiber axons in slice cultures and discovered that filopodial extensions are highly motile. Axonal filopodial motility is actin based and is downregulated with development, although it remains in mature cultures. This motility is correlated with free extracellular space yet is inversely correlated with contact with postsynaptic targets, indicating a potential role in synaptogenesis. Filopodial motility is differentially regulated by kainate receptors: synaptic stimulation of kainate receptors enhances motility in younger slices, but it inhibits it in mature slices. We propose that neuronal activity controls filopodial motility in a developmentally regulated manner, in order to establish synaptic contacts in a two-step process. A two-step model of synaptogenesis can also explain the opposite effects of neuronal activity on the motility of dendritic protrusions.     

Seminal plasma affects membrane integrity and motility of equine spermatozoa after cryopreservation

Effects of seminal plasma on post-thaw motility and membrane integrity of cryopreserved horse spermatozoa were investigated. Carboxyfluorescein diacetate staining was used for the assessment of sperm membrane integrity. Adding 30% of seminal plasma from stallions with high post-thaw sperm motility to ejaculates from stallions with low post-thaw sperm motility increased progressive motility from 24.0 +/- 1.6 to 34.5 +/- 1.9% (P < 0.05) and membrane integrity from 27.0 +/- 2.1 to 34.3 +/- 2.3% membrane-intact spermatozoa (P < 0.05). Conversely, the addition of seminal plasma from stallions with low post-thaw sperm motility to ejaculates from stallions with high post-thaw motility decreased progressive motility from 36.0 +/- 1.6 to 30.0 +/- 2.7% (P < 0.05) but did not induce changes in membrane integrity. Seminal plasma from stallions with opposite post-thaw motility therefore clearly influenced the resistance of spermatozoa to the freezing and thawing process. We conclude that the individual composition of seminal plasma affects the suitability of stallions for semen cryopreservation.     

Acquisition,initiation and maintenance of sperm motility in the shark,Triakis scyllia

Shark sperm were immotile in the testis, but motile in the vesicula seminalis, suggesting that motility potential is acquired in the male reproductive tract. Although sperm acquired motility, they were immobile in the undiluted semen, however, motility occurred upon dilution of the semen in electrolyte solutions, whose concentrations are the same as seawater or uterus fluid, suggesting that exposure to these fluids at ejaculation causes the initiation of sperm motility. Duration of sperm motility was longer in glucose-rich uterus fluid than glucose-free media, suggesting the important role of hexose for maintaining sperm motility in the female reproductive tract.     

Calcium/calmodulin and cAMP/protein kinase-A pathways regulate sperm motility in the stallion

In spite of the importance of sperm motility to fertility in the stallion, little is known about the signaling pathways that regulate motility in this species. In other mammals, calcium/calmodulin signaling and the cyclic AMP/protein kinase-A pathway are involved in sperm motility regulation. We hypothesized that these pathways also were involved in the regulation of sperm motility in the stallion. Using immunoblotting, calmodulin and the calmodulin-dependent protein kinase II β were shown to be present in stallion sperm and with indirect immunofluorescence calmodulin was localized to the acrosome and flagellar principal piece. Additionally, inhibition of either calmodulin or protein kinase-A significantly reduced sperm motility without affecting viability. Following inhibition of calmodulin, motility was not restored with agonists of the cyclic AMP/protein kinase-A pathway. These data suggest that calcium/calmodulin and cyclic AMP/protein kinase-A pathways are involved in the regulation of stallion sperm motility. The failure of cyclic AMP/protein kinase-A agonists to restore motility of calmodulin inhibited sperm suggests that both pathways may be required to support normal motility.     

Alteration of antral and proximal colonic motility induced by chronic psychological stress involves central urocortin 3 and vasopressin in rats

Because of the difficulties in developing suitable animal models, the pathogenesis of stress-induced functional gastrointestinal disorders is not well known. Here we applied the communication box technique to induce psychological stress in rats and then examined their gastrointestinal motility. We measured upper and lower gastrointestinal motility induced by acute and chronic psychological stress and examined the mRNA expression of various neuropeptides in the hypothalamus. Chronic psychological stress disrupted the fasted motility in the antrum and accelerated motility in the proximal colon. mRNA expression of AVP, oxytocin, and urocortin 3 was increased by chronic psychological stress. Intracerebroventricular (ICV) injection of urocortin 3 disrupted the fasted motility in the antrum, while ICV injection of Ucn3 antiserum prevented alteration in antral motility induced by chronic psychological stress. ICV injection of AVP accelerated colonic motility, while ICV injection of SSR 149415, a selective AVP V1b receptor antagonist, prevented alteration in proximal colonic motility induced by chronic psychological stress. Oxytocin and its receptor antagonist L 371257 had no effect on colonic motility in either the normal or chronic psychological stress model. These results suggest that chronic psychological stress induced by the communication box technique might disrupt fasted motility in the antrum via urocortin 3 pathways and accelerates proximal colonic motility via the AVP V1b receptor in the brain.     

癌细胞运动与迁移的分子机制

癌细胞运动和迁移的分子机制远较我们想象的复杂,癌细胞的运动和迁移性和接触性刺激相应答的细胞膜突起形成所启动的多步骤过程的结果.人们普遍想相信,片状伪足在驱动癌细胞迁移中起着主要作用,它通过附着在基底膜上而产生拉动细胞体向前的力量.近来的研究证明,切丝蛋白是癌细胞运动和迁移的一个重要调节因子, 切丝蛋白的局部激活可以诱导片状伪足的形成,并设定细胞运动方向.此外,成束蛋白.Arp2/3复合物、Cdc42、LIM激酶和黏着斑激酶常常协同调节癌细胞的运动和迁移.虽然调节癌细胞运动和迁移的信号通路和分子机制尚未完全阐明,但现有的资料清楚地表明,抑制癌细胞的迁移性将可能成为抑制恶性肿瘤生长和扩散的一个有用的策略.     

Oxidation of glyceraldehyde-3-phosphate dehydrogenase decreases sperm motility

The relation between the activity of the sperm-specific glyceraldehyde-3-phosphate dehydrogenase (GAPDS) and the motility of sperms was investigated. It was found that the mean value of GAPDS activity in sperm samples with low motility is 2.5–3-fold lower than that in samples with high motility. Sperm motility was shown to diminish in the presence of superoxide anion, hydroxyl radical, and hydrogen peroxide. The decrease in sperm motility in the presence of hydrogen peroxide was proportional to the concentration of the oxidant and correlated with the decrease in GAPDS activity (r = 0.96). Based on the literature data on the importance of GAPDS for the motility of sperms together with the presented observations, it was concluded that the decrease in the sperm motility in the presence of reactive oxygen species is due to the oxidation of GAPDS and inhibition of glycolysis.     

Developmental regulation of spine and filopodial motility in primary visual cortex: reduced effects of activity and sensory deprivation

Dendritic protrusions are highly motile during postnatal development. Although spine morphological plasticity could be associated with synaptic plasticity, the function of rapid spine/filopodial motility is still unknown. To investigate the role of spine motility in the development of the visual cortex and its relation with critical periods, we used two-photon imaging of neurons from layers receiving visual input in developing mouse primary visual cortex and compared motility between control and visually deprived animals. Spine and filopodia motility was prominent during early synaptogenesis (P11-P13) but greatly decreased after P15. This "switch" was coincident with a 2.5-fold increase in protrusion density and spine formation. Spine motility was not regulated during the critical period for monocular deprivation (P19-P34). Moreover, delaying the critical period by dark rearing did not delay the normal developmental decrease of spine motility, but caused a modest further reduction in motility at P28-P35. Dark rearing and enucleation also mildly reduced spine motility before eye opening and dark rearing reduced the proportion of filopodia. We conclude that (1) rapid spine motility is not related to critical period plasticity, but is likely to play a role in early synaptogenesis, and (2) neuronal activity stimulates spine motility during synaptogenesis and promotes the appearance of dendritic filopodia.     

A simple cell motility assay demonstrates differential motility of human periodontal ligament fibroblasts, gingival fibroblasts, and pre-osteoblasts

During periodontal regeneration, multiple cell types can invade the wound site, thereby leading to repair. Cell motility requires interactions mediated by integrin receptors for the extracellular matrix (ECM), which might be useful in guiding specific cell populations into the periodontal defect. Our data demonstrate that fibroblasts exhibit differential motility when grown on ECM proteins. Specifically, gingival fibroblasts are twice as motile as periodontal ligament fibroblasts, whereas osteoblasts are essentially non-motile. Collagens promote the greatest motility of gingival fibroblasts in the following order: collagen III>collagen V>collagen I. Differences in motility do not correlate with cell proliferation or integrin expression. Osteoblasts display greater attachment to collagens than does either fibroblast population, but lower motility. Gingival fibroblast motility on collagen I is generally mediated by α2 integrins, whereas motility on collagen III involves α1 integrins. Other integrins (α10 or α11) may also contribute to gingival fibroblast motility. Thus, ECM proteins do indeed differentially promote the cell motility of periodontal cells. Because of their greater motility, gingival fibroblasts have more of a potential to invade periodontal wound sites and to contribute to regeneration. This finding may explain the formation of disorganized connective tissue masses rather than the occurrence of the true regeneration of the periodontium. This research was supported by the Louisiana Board of Regents through the Millennium Trust Health Excellence Fund, HEF-(2000-05)-04.