Myosin VI is required for sorting of AP-1B-dependent cargo to the basolateral domain in polarized MDCK cells.
In polarized epithelial cells, newly synthesized membrane proteins are delivered on specific pathways to either the apical or basolateral domains, depending on the sorting motifs present in these proteins. Because myosin VI has been shown to facilitate secretory traffic in nonpolarized cells, we investigated its role in biosynthetic trafficking pathways in polarized MDCK cells. We observed that a specific splice isoform of myosin VI with no insert in the tail domain is required for the polarized transport of tyrosine motif containing basolateral membrane proteins. Sorting of other basolateral or apical cargo, however, does not involve myosin VI. Site-directed mutagenesis indicates that a functional complex consisting of myosin VI, optineurin, and probably the GTPase Rab8 plays a role in the basolateral delivery of membrane proteins, whose sorting is mediated by the clathrin adaptor protein complex (AP) AP-1B. Our results suggest that myosin VI is a crucial component in the AP-1B-dependent biosynthetic sorting pathway to the basolateral surface in polarized epithelial cells.
Au
Josephine Sui-Yan
JS
Medical Research Council Laboratory of Molecular Biology, Cambridge CB2 2QH, England, UK.
Puri
Claudia
C
Ihrke
Gudrun
G
Kendrick-Jones
John
J
Buss
Folma
F
D033961:Adaptor Protein Complex 1 / Q000378:metabolism*; D020816:Amino Acid Motifs; D000818:Animals; D018797:Cell Cycle Proteins; D002460:Cell Line; D016764:Cell Polarity; D004285:Dogs; D011992:Endosomes / Q000378:metabolism; D006801:Humans; D008562:Membrane Glycoproteins / Q000378:metabolism; D026901:Membrane Transport Proteins; D016297:Mutagenesis, Site-Directed; D018995:Myosin Heavy Chains / Q000032:analysis / Q000737:chemistry / Q000502:physiology*; D020033:Protein Isoforms / Q000032:analysis / Q000737:chemistry / Q000502:physiology; D021381:Protein Transport / Q000502:physiology; D035582:Transcription Factor TFIIIA / Q000378:metabolism; D014759:Viral Envelope Proteins / Q000378:metabolism
D033961:Adaptor Protein Complex 1; D018797:Cell Cycle Proteins; C028391:G protein, vesicular stomatitis virus; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; C409460:OPTN protein, human; D020033:Protein Isoforms; D035582:Transcription Factor TFIIIA; D014759:Viral Envelope Proteins; C089785:myosin VI; D018995:Myosin Heavy Chains