title: Integrin-associated Lyn kinase promotes cell survival by suppressing acid sphingomyelinase activity.
abstract: Integrins govern cellular adhesion and transmit signals leading to activation of intracellular signaling pathways aimed to prevent apoptosis. Herein we report that attachment of oligodendrocytes (OLs) to fibronectin via alpha(v)beta(3) integrin receptors rendered the cells more resistant to apoptosis than the cells attached to laminin via alpha(6)beta(1) integrins. Investigation of molecular mechanisms involved in alpha(v)beta(3) integrin-mediated cell survival revealed that ligation of the integrin with fibronectin results in higher expression of activated Lyn kinase. Both in OLs and in the mouse brain, Lyn selectively associates with alpha(v)beta(3) integrin, not with alpha(v)beta(5) integrin, leading to suppression of acid sphingomyelinase activity and preventing ceramide-mediated apoptosis. In OLs, knockdown of Lyn with small interfering RNA resulted in OL apoptosis with concomitant accumulation of C(16)-ceramide due to activation of acid sphingomyelinase (ASMase) and sphingomyelin hydrolysis. Knocking down ASMase partially protected OLs from apoptosis. In the brain, ischemia/reperfusion (IR) triggered rearrangements in the alpha(v)beta(3) integrin-Lyn kinase complex leading to disruption of Lyn kinase-mediated suppression of ASMase activity. Thus, co-immunoprecipitation studies revealed an increased association of alpha(v)beta(3) integrin-Lyn kinase complex with ionotropic glutamate receptor subunits, GluR2 and GluR4, after cerebral IR. Sphingolipid analysis of the brain demonstrated significant accumulation of ceramide and sphingomyelin hydrolysis. The data suggest a novel mechanism for regulation of ASMase activity during cell adhesion in which Lyn acts as a key upstream kinase that may play a critical role in cerebral IR injury.
authors.affiliation: Department of Neuroscience, Medical University of South Carolina, Charleston, South Carolina 29425, USA.
authors.forename: Daria A
authors.initials: DA
authors.lastname: Chudakova
authors.forename: Youssef H
authors.initials: YH
authors.lastname: Zeidan
authors.forename: Brian W
authors.initials: BW
authors.lastname: Wheeler
authors.forename: Jin
authors.initials: J
authors.lastname: Yu
authors.forename: Sergei A
authors.initials: SA
authors.lastname: Novgorodov
authors.forename: Mark S
authors.initials: MS
authors.lastname: Kindy
authors.forename: Yusuf A
authors.initials: YA
authors.lastname: Hannun
authors.forename: Tatyana I
authors.initials: TI
authors.lastname: Gudz
mesh_terms: D000818:Animals; D002470:Cell Survival; D039121:Integrin alpha6beta1 / Q000378:metabolism; D039302:Integrin alphaVbeta3 / Q000378:metabolism; D016023:Integrins / Q000378:metabolism*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008954:Models, Biological; D034741:RNA, Small Interfering / Q000378:metabolism; D051381:Rats; D019030:Receptors, Vitronectin / Q000378:metabolism; D015427:Reperfusion Injury; D013108:Sphingomyelin Phosphodiesterase / Q000378:metabolism*; D019061:src-Family Kinases / Q000378:metabolism*
chemical_list: D039121:Integrin alpha6beta1; D039302:Integrin alphaVbeta3; D016023:Integrins; D034741:RNA, Small Interfering; D019030:Receptors, Vitronectin; C064660:integrin alphaVbeta5; C060902:lyn protein-tyrosine kinase; D019061:src-Family Kinases; C112980:acid sphingomyelinase-1; D013108:Sphingomyelin Phosphodiesterase