Probable Mechanisms Underlying Interallelic Complementation and Temperature-Sensitivity of Mutations at the shibire Locus of Drosophila melanogaster

Corresponding author: Mani Ramaswami, Department of Molecular and Cellular Biology, Life Sciences South Bldg., Box 210106, University of Arizona, Tucson, AZ 85721, mani{at}u.arizona.edu (E-mail).

Communicating editor: T. W. CLINE

The shibire locus of Drosophila melanogaster encodes dynamin, a GTPase required for the fission of endocytic vesicles from plasma membrane. Biochemical studies indicate that mammalian dynamin is part of a complex containing multiple dynamin subunits and other polypeptides. To gain insight into sequences of dynamin critical for its function, we have characterized in detail a collection of conditional and lethal shi alleles. We describe a probable null allele of shi and show that its properties are distinct from those of two classes of lethal alleles (termed I and II) that show intergroup, interallelic complementation. Sequenced class I alleles, which display dominant properties, carry missense mutations in conserved residues in the GTPase domain of dynamin. In contrast, the sequenced class II alleles, which appear completely recessive, carry missense mutations in conserved residues of a previously uncharacterized "middle domain" that lies adjacent to the GTPase region. These data suggest that critical interactions mediated by this middle domain are severely affected by the class II lethal mutations; thus, the mutant sequences should be very useful for confirming the in vivo relevance of interactions observed in vitro. Viable heteroallelic combinations of shi lethals show rapid and reversible temperature-sensitive paralytic phenotypes hitherto only described for the ts alleles of shi. When taken together with the molecular analysis of shi mutations, these observations suggest that the GTPase domain of dynamin carries an intrinsically temperature-sensitive activity: hypomorphic mutations that reduce this activity at low temperatures result in conditional temperature-sensitive phenotype. These observations explain why screens for conditional paralytic mutants in Drosophila inevitably recover ts alleles of shi at high frequencies.

This article has been cited by other articles:

				R. Narayanan, M. Leonard, B. D. Song, S. L. Schmid, and M. Ramaswami An internal GAP domain negatively regulates presynaptic dynamin in vivo: a two-step model for dynamin function J. Cell Biol., April 11, 2005; 169(1): 117 - 126. [Abstract] [Full Text] [PDF]

				A. Guha, V. Sriram, K. S. Krishnan, and S. Mayor shibire mutations reveal distinct dynamin-independent and -dependent endocytic pathways in primary cultures of Drosophila hemocytes J. Cell Sci., August 15, 2003; 116(16): 3373 - 3386. [Abstract] [Full Text] [PDF]

				A. D. Rogat and K. G. Miller A role for myosin VI in actin dynamics at sites of membrane remodeling during Drosophila spermatogenesis J. Cell Sci., March 14, 2003; 115(24): 4855 - 4865. [Abstract] [Full Text] [PDF]

				D. T. Stimson, P. S. Estes, S. Rao, K. S. Krishnan, L. E. Kelly, and M. Ramaswami Drosophila Stoned Proteins Regulate the Rate and Fidelity of Synaptic Vesicle Internalization J. Neurosci., May 1, 2001; 21(9): 3034 - 3044. [Abstract] [Full Text] [PDF]

				A. Cadavid, A Ginzel, and J. Fischer The function of the Drosophila fat facets deubiquitinating enzyme in limiting photoreceptor cell number is intimately associated with endocytosis Development, January 4, 2000; 127(8): 1727 - 1736. [Abstract] [PDF]

				M. T. Hamblin and M. Veuille Population Structure Among African and Derived Populations of Drosophila simulans: Evidence for Ancient Subdivision and Recent Admixture Genetics, September 1, 1999; 153(1): 305 - 317. [Abstract] [Full Text]

				E. Smirnova, D.-L. Shurland, E. D. Newman-Smith, B. Pishvaee, and A. M. van der Bliek A Model for Dynamin Self-assembly Based on Binding Between Three Different Protein Domains J. Biol. Chem., May 21, 1999; 274(21): 14942 - 14947. [Abstract] [Full Text] [PDF]

				D. T. Stimson, P. S. Estes, M. Smith, L. E. Kelly, and M. Ramaswami A Product of the Drosophila stoned Locus Regulates Neurotransmitter Release J. Neurosci., December 1, 1998; 18(23): 9638 - 9649. [Abstract] [Full Text] [PDF]

				S. E. McGuire, P. T. Le, and R. L. Davis The Role of Drosophila Mushroom Body Signaling in Olfactory Memory Science, August 17, 2001; 293(5533): 1330 - 1333. [Abstract] [Full Text] [PDF]