Novel lipid modifications of secreted protein signals.
Secreted signaling proteins function in a diverse array of essential patterning events during metazoan development, ranging from embryonic segmentation in insects to neural tube differentiation in vertebrates. These proteins generally are expressed in a localized manner, and they may elicit distinct concentration-dependent responses in the cells of surrounding tissues and structures, thus functioning as morphogens that specify the pattern of cellular responses by their tissue distribution. Given the importance of signal distribution, it is notable that the Hedgehog (Hh) and Wnt proteins, two of the most important families of such signals, are known to be covalently modified by lipid moieties, the membrane-anchoring properties of which are not consistent with passive models of protein mobilization within tissues. This review focuses on the mechanisms underlying biogenesis of the mature Hh proteins, which are dually modified by cholesteryl and palmitoyl adducts, as well as on the relationship between Hh proteins and the self-splicing proteins (i.e., proteins containing inteins) and the Hh-like proteins of nematodes. We further discuss the cellular mechanisms that have evolved to handle lipidated Hh proteins in the spatial deployment of the signal in developing tissues and the more recent findings that implicate palmitate modification as an important feature of Wnt signaling proteins.
Mann
Randall K
RK
Department of Molecular Biology and Genetics and Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA. rkmann@jhmi.edu
Beachy
Philip A
PA
D000595:Amino Acid Sequence; D000818:Animals; D019521:Body Patterning; D002784:Cholesterol / Q000737:chemistry; D029721:Drosophila Proteins / Q000737:chemistry* / Q000235:genetics / Q000502:physiology; D004627:Embryonic Induction; D053823:Hedgehog Proteins; D006801:Humans; D008055:Lipids / Q000737:chemistry; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010169:Palmitic Acids / Q000737:chemistry; D011499:Protein Processing, Post-Translational; D021382:Protein Sorting Signals / Q000235:genetics / Q000502:physiology; D011518:Proto-Oncogene Proteins / Q000737:chemistry / Q000502:physiology; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D014018:Tissue Distribution; D015534:Trans-Activators / Q000737:chemistry* / Q000235:genetics / Q000502:physiology; D051153:Wnt Proteins
D029721:Drosophila Proteins; D053823:Hedgehog Proteins; D008055:Lipids; D010169:Palmitic Acids; D021382:Protein Sorting Signals; D011518:Proto-Oncogene Proteins; D015534:Trans-Activators; D051153:Wnt Proteins; C077245:hh protein, Drosophila; D002784:Cholesterol