A beta4 integrin-like protein co-localises with a phosphotyrosine containing protein in the oomycete Achlya bisexualis: inhibition of tyrosine phosphorylation slows tip growth.
We present immunocytochemical data that indicate the presence of, and a close association between beta4 integrin-like proteins and proteins containing phosphorylated tyrosine residues in the oomycete Achlya bisexualis. When hyphae were plasmolysed, these proteins were present in wall-membrane attachment sites where there was also F-actin. A combination of immunoblots, ELISA, and a coupled enzyme assay suggest that phosphorylation may occur by both autophosphorylation and through the action of a tyrosine kinase. Tyrphostins, which are inhibitors of tyrosine kinases, abolished the anti-phosphotyrosine staining, inhibited the kinase activity, slowed tip growth and affected the organisation of the actin cytoskeleton, in a dose-dependent manner. By analogy with the integrins and associated kinases of the metazoa we suggest that these proteins could contribute to the process of tip growth by providing a means of bidirectional signaling between the cell wall and the cytoplasm.
Chitcholtan
Kenny
K
School of Biological Sciences, University of Canterbury, Private Bag 4800, Christchurch 8020, New Zealand.
Garrill
Ashley
A
D044743:Achlya / Q000737:chemistry / Q000254:growth & development* / Q000378:metabolism; D000199:Actins / Q000032:analysis; D020418:Algal Proteins / Q000032:analysis* / Q000737:chemistry; D002462:Cell Membrane / Q000737:chemistry; D002473:Cell Wall / Q000737:chemistry; D004791:Enzyme Inhibitors / Q000494:pharmacology; D025301:Hyphae / Q000737:chemistry / Q000254:growth & development*; D007150:Immunohistochemistry; D039663:Integrin beta4 / Q000032:analysis; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors; D015398:Signal Transduction; D014443:Tyrosine / Q000378:metabolism*; D020032:Tyrphostins / Q000494:pharmacology
D000199:Actins; D020418:Algal Proteins; D004791:Enzyme Inhibitors; D039663:Integrin beta4; D020032:Tyrphostins; D014443:Tyrosine; D011505:Protein-Tyrosine Kinases