Document Detail

An IP3-activated Ca2+ channel regulates fungal tip growth.
MedLine Citation:
PMID:  12432087     Owner:  NLM     Status:  MEDLINE    
Hyphal extension in fungi requires a tip-high Ca(2+) gradient, which is generated and maintained internally by inositol (1,4,5)-trisphosphate (IP(3))-induced Ca(2+) release from tip-localized vesicles and subapical Ca(2+) sequestration. Using the planar bilayer method we demonstrated the presence of two types of IP(3)-activated Ca(2+) channels in Neurospora crassa membranes with different conductances: one low (13 picosiemens), the other high (77 picosiemens). On sucrose density gradients the low conductance channel co-localized with endoplasmic reticulum and plasma membrane, and the high conductance channel co-localized with vacuolar membranes. We correlated the effect of inhibitors on channel activity with their effect on hyphal growth and Ca(2+) gradients. The inhibitor of IP(3)-induced Ca(2+) release, 2-aminoethoxidiphenylborate (2-APB), inhibits both channels, while heparin, 8-(N,N-diethylamino)-octyl-3,4,5-trimethoxybenzoate, hydrochloride (TMB-8) and dantrolene inhibit only the large conductance channel. Because 2-APB inhibits hyphal growth and dissipates the tip-high cytosolic [Ca(2+)] gradient, whereas heparin microinjection, TMB-8 and dantrolene treatments do not affect growth, we suggest that the small conductance channel generates the obligatory tip-high Ca(2+) gradient during hyphal growth. Since IP(3) production must be catalyzed by tip-localized phospholipase C, we show that a number of phospholipase C inhibitors [neomycin, 1-[6-((17beta-3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl]- 1H-pyrrole-2,5-dione (U-73122) (but not the inactive pyrrolidine U-73343), 3-nitrocoumarin] inhibit hyphal growth and affect, similarly to 2-APB, the location of vesicular Ca(2+) imaged by chlortetracycline staining.
Lorelei B Silverman-Gavrila; Roger R Lew
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Journal of cell science     Volume:  115     ISSN:  0021-9533     ISO Abbreviation:  J. Cell. Sci.     Publication Date:  2002 Dec 
Date Detail:
Created Date:  2002-11-14     Completed Date:  2003-07-16     Revised Date:  2007-11-15    
Medline Journal Info:
Nlm Unique ID:  0052457     Medline TA:  J Cell Sci     Country:  England    
Other Details:
Languages:  eng     Pagination:  5013-25     Citation Subset:  IM    
Biology Department, York University, 4700 Keele Street, Toronto, Ontario, M3J 1P3, Canada.
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MeSH Terms
Calcium Channels / physiology*
Inositol 1,4,5-Trisphosphate / physiology*
Lipid Bilayers
Membrane Potentials
Neurospora crassa / growth & development*
Type C Phospholipases / metabolism
Reg. No./Substance:
0/Calcium Channels; 0/Lipid Bilayers; 85166-31-0/Inositol 1,4,5-Trisphosphate; EC 3.1.4.-/Type C Phospholipases

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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