摘要:

AbstractThis study seeks to identity phosphoproteins in axonemes fromParamecium letraureliawhose phosphorylation responses to adenosine 3′,5′‐cyclic monophosphate (cAMP) and Ca2+parallel responses induced by these agents in ciliary behavior in this cell. In purified rxonemes, over 15 bands ranging from Mr>300 kDa to 19 kDa on SDS‐PAGE incorporate32P from adenosine 5′‐γ‐[32P]tri‐phosphate (γ‐32P‐ATP) at pCa 7 in the absence of cAMP. A major band whose label turns over rapidly was identified at Mr 43 kDa. In the presence of 5 μM cAMP, more than eight bands, but not the Mr 43 kDa band, were labeled additionally or enhanced their labeling. These phosphoproteins and their kinases are structural components of the axoneme. Overall, some of the same major bands are labeled in the presence of cAMP in Triton X‐100‐permeabilized paramecia that retain their behavioral responses and in axonemes mechanically isolated from these cells. In particular, two major bands have been identified whose phosphorylation is greatly enhanced by cAMP at low concentrations: (1) a 29 kDa polypeptide whose cAMP‐dependent phosphorylation is diminished at pCa 4 compared with pCa 7 and (2) a 65 kDa polypeptide whose phosphorylation is pCa insensitive. These polypeptides meet minimal criteria for signal‐sensitive regulators of motility para

ISSN:0886-1544    

DOI:10.1002/cm.970120102

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractWe recently purified a calcium‐dependent but calmodulin‐ and phospholipid‐independent protein kinase (CDPK) from cultured plant cells (Harmon et al.:Plant Physiology83:830–837, 1987). A monoclonal antibody (mAb 3B9) directed against CDPK was used to localize this protein inAlliumroot cells andTradescantiapollen tubes using immunofluorescence techniques. The mAb 3B9 staining pattern showed that CDPK is localized within a fibrous network in the cytoplasm resembling the normal interphase network of F‐actin. Treatment of tissue with 10 μM cytochalasin D (CD) prior to fixation abolished the staining pattern. Double‐localization experiments in which pollen tubes were first stained with mAb 3B9 and then with rhodamine‐phalloidin (RP) demonstrated that CDPK and F‐actin were colocalized. Monoclonal antibody 3B9 did not react with purified actin from rabbit muscle orDictyosteliumand did not bind to proteins corresponding to the Mrof actin in crude extracts ofAlliumroot tips andTradescantiapollen tubes.CDPK did not phosphorylate purified rabbit muscle orDictyosteliumactin in vitro. Binding studies showed that CDPK (1) does not cosediment with actin filaments and (2) does not form a complex with G‐actin. The data indicate that although CDPK does not interact directly with actin, it may be associated with an actin‐binding protein and therefore could play a role in the regulation of th

ISSN:0886-1544    

DOI:10.1002/cm.970120103

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractCH12 is a murine B‐cell lymphoma whose surface immunoglobulin (sIg) and concanavalin A (Con A) receptors patch and cap readily. Actin may be involved in CH12 patching and capping, since fodrin and F‐actin collect under the cap, and cytochalasin D inhibits sIg capping. We have examined the state of the actin cytoskeleton during patching and capping. A wide range of concentrations of rabbit anti‐mouse antibody (RAM) and Con A were used to patch or cap CH12 cells. G‐actin was quantitated by DNase I inhibition, F‐actin was quantitated by fluorescence‐activated cell sorter analysis of fluorescent phalloidin staining, and actin nucleation sites were measured by pyrene actin polymerization. None of these methods detected any significant changes in actin when compared to control cells or untreated cells, leading us to conclude that increased actin polymerization is not necessary for capping to occur. The significance of these data to the membrane flow and cytoskeletal models of capping i

ISSN:0886-1544    

DOI:10.1002/cm.970120104

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractMitotic spindles isolated from the diatomStephanopyxis turrisbecome thiophosphorylated in the presence of ATPγS at specific locations within the mitotic apparatus, resulting in a stimulation of ATP‐dependent spindle elongation in vitro. Here, using indirect immunofluorescence, we compare the staining pattern of an antibody against thiophosphorylated proteins to that of MPM‐2, an antibody against mitosis‐specific phosphoproteins, in isolated spindles. Both antibodies label spindle poles, kinetochores, and the midzone. Neither antibody exhibits reduced labeling in salt‐extracted spindles, although prior salt extraction inhibits thiophosphorylation in ATPγS. Furthermore, both antibodies recognize a 205 kd band on immunoblots of spindle extracts. Microtubule‐organizing centers and mitotic spindles label brightly with the MPM‐2 antibody in intact cells. These results show that functional mitotic spindles isolated fromS. turrisare phosphorylated both in vivo and in vitro. We discuss the possible role of phosphorylated cytoskeletal proteins in the control of mitotic spi

ISSN:0886-1544    

DOI:10.1002/cm.970120105

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractTo study the in vivo role of myosin‐II inAcanthamoeba castellanii, motile cells were microinjected with monoclonal antibodies raised against the myosin‐II heavy chain. All injected cells underwent a transient shock response. It was found that although injection of buffer alone or of an endogenousAcanthamoebaprotein decreased the motility of injected cells from 7 μm/min to ∼3 μm/min, injection of monoclonal antibodies specific for myosin‐II decreased motility further to ∼0.8 μm/min. This effect was seen whether or not the monoclonal antibody to myosin‐II inhibited the actomyosin‐II MgATPase activity in vitro. Levels of antibody far in excess of endogenous myosin‐II concentrations could not completely block amoeboid movement. The morphology of moving antimyosin‐II‐injected cells was unusual, suggesting a greater defect in the ability to retract the trailing edge of the cell rather than to extend the leading edge. Endosomes frequently disappeared from injected cells, and although buffer‐injected cells rapidly recovered visible endosomes (50% recovery at 5 min), endosomes were not seen in antimyosin‐II‐injected cells until, on the average, ∼50 min after injection. Injection of a nonspecific antibody or of a nonspecific exogenous protein (ovalbumin) also decreased the mobility of the injected cells beyond that of buffer‐injected cells (to ∼1 μm/min). These cells tended to recover endosomes more rapidly (∼25 min) than cells injected with antimyosin‐II monoclonal antibodies. The inability of antibodies to myosin‐II to inhibit completely any of the movements studied suggests that although myosin‐II probably plays a role in these motilities, the cell either routinely uses or can draw upon another cytoplasmic motor to maintain locomotion, organelle movement, co

ISSN:0886-1544    

DOI:10.1002/cm.970120106

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractA model for slow axonal transport is developed in which the essential features are reversible binding of cytoskeletal elements and of soluble cytosolic proteins to each other and to motile elements such as actin microfilaments. Computer simulation of the equations of the model demonstrate that the model can account for many of the features of the SCa and SCb waves observed in pulse experiments. The model also provides a unified explanation for the increase and decrease of neurofilament transport rates observed in various toxicant‐induced neuropathie

ISSN:0886-1544    

DOI:10.1002/cm.970120107

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

ISSN:0886-1544    

DOI:10.1002/cm.970120108

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

ISSN:0886-1544    

DOI:10.1002/cm.970120101

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY