Human remyelination promoting antibody inhibits apoptotic signaling and differentiation through Lyn kinase in primary rat oligodendrocytes.
OBJECTIVE
Human remyelination promoting IgM mAbs target oligodendrocytes (OLs) and function in animal models of multiple sclerosis (MS). However, their mechanism of action is unknown. This study seeks to identify the cellular mechanism of action of a recombinant human IgM on OL survival.


METHODS
Binding of rHIgM22 to the surface of rat OLs was studied by co-localization with various markers. RHIgM22-mediated effects on apoptotic signaling in OLs, differentiation markers, and signaling molecules were detected by Western blotting and immunoprecipitation.


RESULTS
RHIgM22 co-localized with integrin β3 but not other integrin β-chains in OLs. Downstream of integrin β3 we identified Src family kinase (SFK) Lyn as a key player of rHIgM22-mediated actions in OLs. Lyn immunoprecipitated in a complex together with integrin αvβ3 and PDGFαR. Lyn expression was 9-fold up-regulated and Lyn activation was 3-fold higher inrHIgM22-treated OL cultures compared with controls. RHIgM22 inhibited apoptotic signaling by greater than 10-fold reduction of caspase-3 and capsase-9 cleavage and reduced by 4-fold expression of differentiation markers MBP and MOG in OLs. SFK inhibitors PP2 and SU6656 inhibited Lyn activity and restored caspase-cleavage in OLs. A human IgM that did not promote remyelination and medium wereused as controls.


CONCLUSIONS
rHIgM22 prevented apoptotic signaling andinhibited OL differentiation by Lyn implying thatIgM-mediated remyelination is due toprotection of OPC and OLs rather than promotion of OPC differentiation.
Watzlawik
J
J
Department of Neurology, Mayo Clinic College of Medicine, Rochester, Minnesota 55905, USA.
Holicky
E
E
Edberg
D D
DD
Marks
D L
DL
Warrington
A E
AE
Wright
B R
BR
Pagano
R E
RE
Rodriguez
M
M
D000818:Animals; D000831:Animals, Newborn; D017209:Apoptosis / Q000187:drug effects*; D001921:Brain / Q000166:cytology; D053148:Caspase 3 / Q000378:metabolism; D002454:Cell Differentiation / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D006801:Humans; D007075:Immunoglobulin M / Q000494:pharmacology* / Q000627:therapeutic use; D047468:Immunoprecipitation / Q000379:methods; D007211:Indoles / Q000494:pharmacology; D039661:Integrin beta3 / Q000378:metabolism; D009836:Oligodendroglia / Q000187:drug effects*; D010766:Phosphorylation / Q000187:drug effects; D011247:Pregnancy; D011743:Pyrimidines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D011994:Recombinant Proteins / Q000276:immunology / Q000494:pharmacology / Q000627:therapeutic use; D015398:Signal Transduction / Q000187:drug effects*; D013449:Sulfonamides / Q000494:pharmacology; D019061:src-Family Kinases / Q000378:metabolism*
C412373:AG 1879; D004791:Enzyme Inhibitors; D007075:Immunoglobulin M; D007211:Indoles; D039661:Integrin beta3; D011743:Pyrimidines; D011994:Recombinant Proteins; C416927:SU 6656; D013449:Sulfonamides; C060902:lyn protein-tyrosine kinase; D019061:src-Family Kinases; D053148:Caspase 3