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TIP maker and TIP marker; EB1 as a master controller of microtubule plus ends.

Vaughan KT - J. Cell Biol. (2005)

Bottom Line: EB1 acts as an exquisite marker of dynamic MT plus ends in some cases, whereas in others EB1 is thought to directly dictate the behavior of the plus ends.How EB1 differentiates between these two roles remains unclear; however, a growing list of interactions between EB1 and other MT binding proteins suggests there may be a single mechanism.These results raise the possibility that EB1 is a central player in MT-based transport, and that the activity of MT-binding proteins depends on their ability or inability to interact with EB1.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological Sciences, University of Notre Dame, Notre Dame, IN 46556, USA. Vaughan.4@nd.edu

ABSTRACT
The EB1 protein is a member of the exciting and enigmatic family of microtubule (MT) tip-tracking proteins. EB1 acts as an exquisite marker of dynamic MT plus ends in some cases, whereas in others EB1 is thought to directly dictate the behavior of the plus ends. How EB1 differentiates between these two roles remains unclear; however, a growing list of interactions between EB1 and other MT binding proteins suggests there may be a single mechanism. Adding another layer of complexity to these interactions, two studies published in this issue implicate EB1 in cross-talk between mitotic MTs and between MTs and actin filaments (Goshima et al., p. 229; Wu et al., p. 201). These results raise the possibility that EB1 is a central player in MT-based transport, and that the activity of MT-binding proteins depends on their ability or inability to interact with EB1.

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EB1 as a multi-functional protein involved in cargo transfer. Models proposed by studies in this issue (Goshima et al., 2005; Wu et al., 2005) suggest a more global role for EB1 in cytoskeletal transport. (A) MT tip tracking of melanophillin in an EB1-dependent manner coupled with binding of melanophillin to myosin Va in melanocytes identifies a new function for EB1. In contrast to other models that implicate EB1 in recruitment of proteins involved in MT-based transport, this work potentially identifies a role in transfer of cargo from one cytoskeletal system to another (MTs to actin). (B) Parallel work on MT motors involved in mitotic spindle formation identify a connection between EB1 and ncd at sites where kinetochore fibers (k-fibers) interact with centrosomal MTs (C-MTs) emanating from the spindle poles. EB1 is proposed to play a role in determining where ncd initiates contact between these two MT populations—a role that molecular modeling predicts is essential for the formation of a functional and focused spindle.
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fig2: EB1 as a multi-functional protein involved in cargo transfer. Models proposed by studies in this issue (Goshima et al., 2005; Wu et al., 2005) suggest a more global role for EB1 in cytoskeletal transport. (A) MT tip tracking of melanophillin in an EB1-dependent manner coupled with binding of melanophillin to myosin Va in melanocytes identifies a new function for EB1. In contrast to other models that implicate EB1 in recruitment of proteins involved in MT-based transport, this work potentially identifies a role in transfer of cargo from one cytoskeletal system to another (MTs to actin). (B) Parallel work on MT motors involved in mitotic spindle formation identify a connection between EB1 and ncd at sites where kinetochore fibers (k-fibers) interact with centrosomal MTs (C-MTs) emanating from the spindle poles. EB1 is proposed to play a role in determining where ncd initiates contact between these two MT populations—a role that molecular modeling predicts is essential for the formation of a functional and focused spindle.

Mentions: The conceptual challenge of this work is to determine the function of EB1 and MT binding for melanophillin. Is this a nuance of overexpression or an important clue into the role melanophillin plays in melanosome transport? Interestingly, the authors point out that melanosomes do not tip-track normally, and that the movements of melanosomes are very different from tip-tracking proteins. Furthermore, expression of the tagged melanophillin constructs reveals both MT- and actin-associated structures in the cell periphery. Perhaps this dichotomy is the crucial finding for melanophillin. The authors propose the enticing possibility that melanophillin uses a combination of MT binding (via EB1) and actin binding (via myosin V) to build a transient transfer station in the cell periphery where melanosomes can be efficiently handed from MTs to microfilaments (Fig. 2). This is consistent with the known behaviors of melanosomes (Rogers and Gelfand, 1998) and uncovers a functional aspect of melanophillin that would be difficult to examine due to the transient nature of these intermediates. In common with other EB1 studies, it remains unclear if EB1 serves a role as a marker for MT plus ends that have reached the cell periphery, or if EB1 actively preserves particular MT plus ends long enough to allow the hand-off. However, this work provides compelling evidence that EB1 plays a larger role than previously anticipated.


TIP maker and TIP marker; EB1 as a master controller of microtubule plus ends.

Vaughan KT - J. Cell Biol. (2005)

EB1 as a multi-functional protein involved in cargo transfer. Models proposed by studies in this issue (Goshima et al., 2005; Wu et al., 2005) suggest a more global role for EB1 in cytoskeletal transport. (A) MT tip tracking of melanophillin in an EB1-dependent manner coupled with binding of melanophillin to myosin Va in melanocytes identifies a new function for EB1. In contrast to other models that implicate EB1 in recruitment of proteins involved in MT-based transport, this work potentially identifies a role in transfer of cargo from one cytoskeletal system to another (MTs to actin). (B) Parallel work on MT motors involved in mitotic spindle formation identify a connection between EB1 and ncd at sites where kinetochore fibers (k-fibers) interact with centrosomal MTs (C-MTs) emanating from the spindle poles. EB1 is proposed to play a role in determining where ncd initiates contact between these two MT populations—a role that molecular modeling predicts is essential for the formation of a functional and focused spindle.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2171192&req=5

fig2: EB1 as a multi-functional protein involved in cargo transfer. Models proposed by studies in this issue (Goshima et al., 2005; Wu et al., 2005) suggest a more global role for EB1 in cytoskeletal transport. (A) MT tip tracking of melanophillin in an EB1-dependent manner coupled with binding of melanophillin to myosin Va in melanocytes identifies a new function for EB1. In contrast to other models that implicate EB1 in recruitment of proteins involved in MT-based transport, this work potentially identifies a role in transfer of cargo from one cytoskeletal system to another (MTs to actin). (B) Parallel work on MT motors involved in mitotic spindle formation identify a connection between EB1 and ncd at sites where kinetochore fibers (k-fibers) interact with centrosomal MTs (C-MTs) emanating from the spindle poles. EB1 is proposed to play a role in determining where ncd initiates contact between these two MT populations—a role that molecular modeling predicts is essential for the formation of a functional and focused spindle.
Mentions: The conceptual challenge of this work is to determine the function of EB1 and MT binding for melanophillin. Is this a nuance of overexpression or an important clue into the role melanophillin plays in melanosome transport? Interestingly, the authors point out that melanosomes do not tip-track normally, and that the movements of melanosomes are very different from tip-tracking proteins. Furthermore, expression of the tagged melanophillin constructs reveals both MT- and actin-associated structures in the cell periphery. Perhaps this dichotomy is the crucial finding for melanophillin. The authors propose the enticing possibility that melanophillin uses a combination of MT binding (via EB1) and actin binding (via myosin V) to build a transient transfer station in the cell periphery where melanosomes can be efficiently handed from MTs to microfilaments (Fig. 2). This is consistent with the known behaviors of melanosomes (Rogers and Gelfand, 1998) and uncovers a functional aspect of melanophillin that would be difficult to examine due to the transient nature of these intermediates. In common with other EB1 studies, it remains unclear if EB1 serves a role as a marker for MT plus ends that have reached the cell periphery, or if EB1 actively preserves particular MT plus ends long enough to allow the hand-off. However, this work provides compelling evidence that EB1 plays a larger role than previously anticipated.

Bottom Line: EB1 acts as an exquisite marker of dynamic MT plus ends in some cases, whereas in others EB1 is thought to directly dictate the behavior of the plus ends.How EB1 differentiates between these two roles remains unclear; however, a growing list of interactions between EB1 and other MT binding proteins suggests there may be a single mechanism.These results raise the possibility that EB1 is a central player in MT-based transport, and that the activity of MT-binding proteins depends on their ability or inability to interact with EB1.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological Sciences, University of Notre Dame, Notre Dame, IN 46556, USA. Vaughan.4@nd.edu

ABSTRACT
The EB1 protein is a member of the exciting and enigmatic family of microtubule (MT) tip-tracking proteins. EB1 acts as an exquisite marker of dynamic MT plus ends in some cases, whereas in others EB1 is thought to directly dictate the behavior of the plus ends. How EB1 differentiates between these two roles remains unclear; however, a growing list of interactions between EB1 and other MT binding proteins suggests there may be a single mechanism. Adding another layer of complexity to these interactions, two studies published in this issue implicate EB1 in cross-talk between mitotic MTs and between MTs and actin filaments (Goshima et al., p. 229; Wu et al., p. 201). These results raise the possibility that EB1 is a central player in MT-based transport, and that the activity of MT-binding proteins depends on their ability or inability to interact with EB1.

Show MeSH
Related in: MedlinePlus