beta 1-integrins mediate Ca2+-signalling and T cell spreading via divergent pathways

Interaction of Jurkat T-lymphocytes with two extracellular matrix (ECM) pro teins of the basement membrane, laminin or collagen type IV, combined with poly-l lysine resulted in a strong adhesion, a highly increased intracellul ar Ca(2+-)concentration ([Ca2+](i)), as compared to cells on laminin or col lagen type IV alone and in spreading of the cells. The strong adhesion was independent of an increase in [Ca2+](i), was not mediated by a beta 1-integ rin, and was due to charge interaction between the positively charged polya minoacid and the negatively charged cell surface. The latter was confirmed by substitution of poly-l-lysine by other positively charged polyaminoacids . In contrast, Ca2+-signalling and spreading of the cells adhering to lamin in or collagen type IV combined with poly-L-lysine was completely blocked b y anti-beta 1 mAb. However, spreading of the cells was independent of an in crease in [Ca2+](i) suggesting divergent signal transduction pathways leadi ng to Ca2+-signalling and spreading of the cells. We elucidated these signa l transduction pathways by inhibition of key enzymes involved. The tyrosine kinase inhibitor genistein blocked Ca2+-signalling as well as spreading, w hereas inhibitors of PKC (calphostin C, GF109203x), PLC gamma (U73122) and PLA(2) (bromophenacyl-bromide (BPB), 3-[4-octadecyl)benzoyl]acrylic acid (O BAA)) selectively blocked spreading of the cells. CELL SIGNAL 11;8:611-619, 1999. (C) 1999 Elsevier Science Inc.