Vs. Babiychuk et al., Smooth muscle actomyosin promotes Ca2+-dependent interactions between annexin VI and detergent-insoluble glycosphingolipid-enriched membrane domains, ACT BIOCH P, 47(3), 2000, pp. 579-589
The mechanical link coupling cytoskeletal and contractile proteins to the s
arcolemma of smooth muscle cells is essential for transmitting tension from
the cell's interior to exterior. In addition to the well-characterized act
in-integrin associations present in adhaerens junctions, our recent work ha
s postulated the existence of a reversible annexin-dependent membrane-cytos
keleton complex, forged in response to a rise in intracellular Ca2+ concent
ration following smooth muscle cell stimulation (Babiychuk et al., J. Biol
Chem. 1999, 274, 35191-35195). Detailed biochemical characterization of the
interactions responsible for the formation of this complex revealed that a
nnexins II and VI interact with actomyosin, or detergent-insoluble glycosph
ingolipid-enriched membrane domains (rafts) purified from smooth muscle, in
a concentration- and Ca2+-dependent manner. Annexin If interacted with lip
id rafts with high Ca2+-sensitivity, while for annexin VI this interaction
required non-physiologically high concentrations of free Ca2+. However, the
Ca2+-sensitivity of the latter interaction strongly increased in the prese
nce of purified smooth muscle actomyosin. The detailed biochemical analysis
of the interactions occurring between annexin II, annexin VI, actomyosin a
nd rafts suggests that annexins regulate sarcolemmal organization during sm
ooth muscle cell contraction.