Flotillin microdomains interact with the cortical cytoskeleton to control uropod formation and neutrophil recruitment

Abstract

The association between flotillin microdomains and the cortical cytoskeleton controls myosin IIa activation and neutrophil chemotaxis.

Calpain inhibition prevents flotillin re-ordering and Src family activation during capacitation

“…The above results indicated that flotillin microdomains underwent a re-ordering triggered by capacitation in the guinea p i g sper m. Sub seque ntly, w e pe rformed coimmunoprecipitation assays to determine whether spectrin and flotillin-1 were associated in the guinea pig sperm, as proposed in other cell types (Head et al 2014;Ludwig et al 2010;Salzer and Prohaska 2001). The Western blot analysis of co-immunoprecipitated proteins revealed that spectrin coimmunoprecipitated together with flotillin-1 in noncapacitated sperm, whereas in capacitated sperm, a significantly lower amount of spectrin co-immunoprecipitated with flotillin-1 (Fig.…”

“…We have shown that, by inhibiting spectrin cytoskeleton cleavage via calpain, the normal course of the acrosome reaction is blocked in guinea pig sperm (Bastian et al 2010). Interestingly, flotillin microdomains have the property of spatially organizing the plasma membrane and allowing specifically located signaling (i.e., active SFKs) by interacting with the cell cortical cytoskeleton, specifically with actin, spectrin and myosin 2a (Langhorst et al 2007;Ludwig et al 2010). Significant aggregation of flotillin-1 in the apical acrosomal region has been reported as being a capacitation marker in boar sperm (van Gestel et al 2005); however, the mechanisms regulating such an aggregation and its involvement in capacitation and the acrosome reaction have not been fully elucidated.…”

“…Spectrin forms a submembranous cytoskeleton comprising α-and β-subunits assembled in antiparallel filamentous heterodimers. The spectrin cytoskeleton is linked to the plasma membrane through ankyrin (Bennett and Healy 2009); however, novel evidence strongly suggests that spectrin associates with membrane domains by means of flotillins in red blood cells and neutrophils (Head et al 2014;Ludwig et al 2010;Salzer and Prohaska 2001). The relationship between the spectrin cytoskeleton and flotillins is still poorly understood.…”

How reggies regulate regeneration and axon growth

“…However, this view was challenged since other investigators could not find a reggie-dependent endocytosis of GPI-anchored proteins nor was the emergence of caveola-like indentationsreported to be formed in Hela cells after reggie-1 and -2 overexpression for endocytosis (Frick et al 2007)-observed by other laboratories (Kirkham et al 2008;Langhorst et al 2008a;Lundmark et al 2008;Schneider et al 2008; and our own unpublished data). Also, the recently published reggie-2 knock-out mouse did not show the expected defect (Ludwig et al 2010). From our point of view, several observations speak for a reggie-mediated cargo transport (which includes the recycling compartment) towards the plasma membrane.…”

“…Our own unpublished work has demonstrated that expression of dominant-negative forms of specific Rho-GTPases, which co-exist with reggies on specific tubules and vesicles and regulate vesicle sorting and trafficking, causes loss of reggie from these tubules/vesicles and promotes delivery of reggie to lysosomes. It has, moreover, been observed that downregulation of reggie-1 in Hela and N2a cells by siRNAs leads to the degradation of reggie-2 (Solis et al 2007) while others have reported vice versa (Ludwig et al 2010). Together with the fact that reggies form homo-and hetero-oligomers, their joined up-and downregulation suggests that they are perhaps scaffolds of a dynamic tubulo-vesicular compartment whose abundance and efficacy seems to depend on the available concentration of reggie-1 and reggie-2.…”