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A.C. Dose, A.C. Corsa, B. Burnside; Phosphoinositide Binding to the Tail Domain of the Myosin Myo3A of Vertebrate Photoreceptors . Invest. Ophthalmol. Vis. Sci. 2006;47(13):5527.
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© ARVO (1962-2015); The Authors (2016-present)
The tail of Myo3A, a myosin which localizes to the calycal processes in bass rod and cone photoreceptors binds to several phosphoinositides, including (4,5) bis–phosphate (PI(4,5)P2), via at least two binding sites in its tail region. These studies examine these interactions further and seek to determine whether the phospholipid PI(4,5)P2 colocalizes with Myo3A in photoreceptor calycal processes.
Myo3A tail and PI(4,5)P2 interactions were tested initially using PIP strips in which various PIP’s are immobilized on a membrane and probed with several Myo3A tail fusion protein constructs. In order to quantitatively compare the Myo3A tail affinity for different lipids, PIP arrays were used. PIP coated beads were also used to confirm the interaction between Myo3A tail and (PI(4,5)P2). An antibody raised against PI(4,5)P2 was used to immunolocalize PI(4,5)P2 in isolated teleost rod and cone photoreceptors.
Myo3A tail fragments recognized PI(3,4)P2, PI(4,5)P2, PI(3,5)P2, and PI(3,4,5)P3 on PIP strips. PIP arrays demonstrated that PI(4,5)P2 was recognized at a higher affinity than PI(3,4)P2 and PI(3,4,5)P3 but lower affinity than PI(3,5)P2. The tail of Myo3A bound to beads coated with PI(4,5)P2 confirming this interaction. However, we saw no evidence that Myo3A binding concentrated PI(4,5)P2 in photoreceptor calycal processes using an anti–PI(4,5)P2 immunocytochemistry, rather immunulabeling was concentrated in the accessory outer segment in cones and the axoneme in rods.
Myo3A tail fragments from the IQ domain–rich region of the tail bind to four phosphoinositides, including PI(4,5)P2. PI(4,5)P2 is not concentrated in calycal processes like Myo3A but concentrates in rod axonemes and cone accessory outer segments.
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